With any of us, striking through the clear is ALWAYS on our minds. We are all very consious about our limitations(the paint), and unless you fork over some serious dough for a high dollar paint depth guage that seperates primer, base and clear levels, you will never really know exactly what you have to work with(clear coat). Affordable paint depth guages will only read total thickness from the top of the sheet metal to the top of the clear(example 4.5 Mils total thickness). You will never know exactly how thick the clear is(and the clear is all you are working with).
Best advice I can give you is to buy the best paint depth guage you can afford, and use it to
monitor your work as you go. Take a measurement, work the area, take another measuremement, then work a bit more, etc... Monitor how much you are removing. Every paint is different, and reacts to sanding, coumpounding, polishing differently. Buying a paint guage to monitor your progress will inform you exactly how much you are removing from the area.
For me, my magic number is .5 Mils. That is the most I will remove from an unknown paint source. If I know the car has just been painted, and I know(for a fact) that the painter laid on enough clear, then I will go a bit further, if needed.
Also, another good tool for yourself is to ask your customer questions(if you're dealing with a customer). I recently just turned down a very high dollar wet sanding job on a 1st gen Dodge Viper(would have been about an $1500 job). I educated myself about the paint's life by asking my customer questions. He answered all of my questions honestly, and I found out that he's had the paint buffed 6 times in it's life. For me, it was too risky of a job, so I passed on the wet sanding, and took a bit of time to educate the customer about paint, and just how thin it is. In the end, he has hired me to polish it. Which I am completely confident I can do successfully.
Something to always keep in the back of your mind when it comes to wet sanding, buffing and polishing. On a normal factory paint job, the clear coat is thinner than a sheet of paper.
Just my $0.02
Nick
Ninja Edit: Just read your signature, and with 30 years of experience, I'm sure I didn't tell you anything that you didn't already know. Your post just kind of sounded like you were a bit new to all of this, and was explaining myself in detail. Sorry if I offended you.
