In answer to the buffing question:

When you use an enamel paint, typically you shoot 3-4 coats. With the 2 stage (base clear), typically the clear coat is also applied around 4 coats.

As a beginner painter, I found I would either sand a little too deep or when buffing, burn through an edge when I color sanded an enamel finish. As I did more work, I learned when and where to sand and buff to get the best finish. It does take some finesse. Fixing those mistakes are where the big difference comes into play.

Clear coat is more forgiving when you make a mistake sanding or buffing. Usually you only have to re-clear the affected panel and not the entire side, or have to deal with blending color into the next panels as you might have to do with enamel paints.

Also, if you are using the 2 stage system, you can apply a few more coats of clear than normal and give yourself a little more room for sanding later on. Another nice feature is laying on a few coats of clear, sanding it with a 600 grit, then spraying a few more coats of clear. After that has dried, sand with 1500 or 2000 grit and buff as usual. This will give you that deep mirror finish similar to the old style laquer/clear paint jobs.

With single stage, you really don't have the same options. You can add a few more coats but generally it is not recommended to go too thick. If you do it dries funny in some cases, and also can lead to sagging much easier.

When buffing, especially for a first timer, use the foam system from 3M or a similar product. The foam pads will not burn through the paint in most cases. Yes, you can burn through if you try or get really careless, but generally not a worry and they are excellent to use. Now, wool pads on the other hand work well, but you generate more heat with wool and can burn through an edge very quickly.

Compounds for buffing differ greatly as well. I usually use the Finesse-it (3M again) brand. There are 2 stages, one is a compound used after cutting (color sanding), then the second stage is a polish to bring out the shine. After that, use a swirl remover which really shines it up nice. After properly curing you can start with the waxes, glazes etc.

There are many different products available for buffing. Meguires has some nice stuff, Wizards makes some as well. Find one you like or ask around to get opinions before buying, then stick with the entire line of products to get the best results. Mixing brands usually brings unpredictable results.

This stuff is not cheap, especially when outfitting for foam the first time. Make sure to get good quality first, then worry about cost. You will appreciate the difference it makes.