Whether you are a professional detailer or a "weekend warrior" (DIY detailer) machine polishing your car can either be a fun & enjoyable project or a frustrating experience. Often the difference comes down to picking the right product(s). In most cases the determining factor in what products you pick (combination of product + pads) is how fast the scratches are removed. For professional detailers time is money so picking products to get the job done as quickly as possible impacts the profit you make on the job. Conversely a DIY polisher is not under such time constraints to get the job done in a hurry so does not need to be as "aggressive" removing paint defects.
Remember, even the lightest, least aggressive polish out there has the ability to remove clear coat... it just takes much longer to do so than with a more aggressive compound. If you are not skilled (or have a low comfort level using a buffer) don't be intimidated. Just choose a less aggressive pad and product combination to remove the scratches. It may take a little longer but the results will be the same.
Note to the Pros: Do a test area! It's hilarious when we get a customer in the store that says "this weekend I am polishing a 1989 Ford Mustang, its red. What compound should I use?" Huh? Just think about the combinations of makes, models & model years of vehicles there are. Even the best polisher in the world has not memorized the clear coat hardness of every vehicle out there. And the best polishers know they do not have to! Pick what you think is the correct pad/product combination & try it on a section of the car. If the scratches immediately disappear you can move to a lighter pad and/or product so as to not remove more clear cut than you have to. Keep in mind that the goal is to get the defects removed from the paint while removing as little of the clear coat as you need to. If you have done 3 or 4 passes over the test area and still see scratches you should move up to a more aggressive combination of product/pad to speed up the job. It really is that simple. That is why it is important for a pro to have multiple combinations of compounds and pads at their disposal when starting a job. A plumber doesn't show up to a job with one wrench in his toolbox. You shouldn't either.
The "standard" method of polishing a car has always been to compound first to remove heavy paint defects and then polish after to refine the shine & remove any minor paint damage (often referred to as marring) caused during the compound stage. However with the number of quality products now available it is often possible to complete the job in one stage (one product & one pad). This makes car polishing for the DIY guy a much simpler and enjoyable project.
Pad selection is a part of this whole process as well. Just always match up the type of pad you use with the type of product. IE: it makes no sense to use a heavy cut compound with a light polishing pad. Or vice versa why use a polish with a heavy cut wool pad?
Heavy Cut Compounds
Heavy cut compounds are the most aggressive compound and are the fastest at removing scratches. They are mostly used by professional polishers on heavily damaged paint. Heavy cut compounds should be followed up by a polish.
Cutting compounds are also designed to remove moderate to heavy damage from paint. Although not as aggressive as heavy cut compounds they still have the ability to remove deeper scratches fairly quickly. Most often cutting compounds are followed up with a second (polishing) stage.
All-in-One's are just as the name implies. The compound and polish stages are combined in one product. As the product moves over the surface the abrasives (scratch removers) break down and the product turns into a polish. This of particular benefit to DIY'ers. Although not as fact acting as a dedicated compound, they still have the ability to remove scratches and leave a nice shine behind. If you don't mind spending a bit more time removing defects an all-in-one can greatly simplify the process of restoring your paint. And often the extra time spent doing a few extra passes on the paint to get all the defects out is gained back by not having to do a second stage polish.
Although much less aggressive than a compound, a polish does still have the ability to remove clear coat. A polish is used as a second step in 2 stage compound/polish. They are used after the compound has removed the deep scratches to remove any remaining marring or buffing swirls caused by the more aggressive compound. A polish can also be used on paint that has little to no defects (scratches). A polish will remove just enough clearcoat to expose a fresh layer of paint thus enhancing the shine. Often before applying a coating on a car (even with no paint defects) a polish is done to ensure the coating is going on the shiniest & cleanest surface possible.
Jewelling polishes or Ultra-Fine polishes are very fine polishes used as a final step polish. They are applied using a buffer at a very low speed. Reality is the enhanced shine they provide will probably not be noticeable to the naked eye but they do bring out the depth of colour in the paint. Jewelling is not commonly performed during most polishing jobs and is usually performed as an example on a show car right before a car show and are not really of benefit to daily driven cars.
Coating Prep Polishes
As ceramic coatings have become more and more mainstream (and easier to apply by the DIY'er) so have related prep and maintenance products. A coating prep polish contains the same Sio2 particles that are in ceramic coatings. They can be used in several ways. One of the most common is to use a prep polish as a final polishing step before applying a coating. The Sio2 particles in the polish that are left behind on the paint help your coating to bond better to the paint surface. Another common use for these polishes is to "repair" a damaged coating (Essence + is a great choice for coating repair). If you have a scuff or light scratches in your coating you can buff it out with a coating polish & leave a layer of Si02 behind.
Getting a scuff or isolated scratch is almost inevitable on a daily driven car. These isolated defects can often be removed by hand with a scratch remover. Just use a foam wax applicator pad. Apply the scratch remover to the pad and rub the pad over the defect in a circular motion. Periodically wipe the compound off and check the results. You may need to repeat the process several times. Remember that if you can feel a scratch with your fingernail it is too deep to fully remove (it has penetrated through the clearcoat).