This will always depend on the aggressiveness of the 'combo' - the combination of pad and compound/polish, you use with your DPX or MPX machine. This is because a combo with more cut will take away more of the top layer to level it down to the bottom of the deepest defect, essentially making the defect disappear. As a general rule of thumb though, a heavy cutting combo will take away approximately 5-6 microns and a fine refining polish around 1-2 microns of the top layer of paint or lacquer. To put this into context a human hair is around 70 microns thick, and average two stage OEM paintwork around 100-140 microns thick, including a clearcoat layer (the bit you're polishing away) of around 45-70 microns. Single stage paintwork (topcoat without lacquer) is a little thinner and often softer, but again you're only taking away a tiny amount when polishing a panel. On the vast majority of cars there will be plenty of clearcoat to polish, strike through - or burning through the top layer - only really happens due to poor techniques, or on older vehicles which have been repeatedly machine polished over the course of decades. Although the key is only to polish when your vehicle really needs it for enhancement or defect removal, it's highly unlikely that you'll be polishing through your paintwork. As for what combo to use for different types of defects including the dreaded swirl marks,... Well, we've made that straightforward by developing our range of colour-coded compounds and pads specifically for use with our dual action polishers. These include our Revitalise System V2, (with all machine polishing compounds and pads available separately), and One Step All-in-One Compound. For more on those, and all the essential information about how polishes and compounds work, see our guide: All Car Polishes Explained.