I don't have much experience with the 2part clears, but when I was painting guitars, I would go back and forth between Acrylic Lacquer from Duplicolor, and Nitro Cellulose Lacquer from different manufacturers. (Not on the same project... you can't mix the nitro and acrylic lacquers... they don't like each other.) But the prinicpals are the same. You should dust on the first layer as this will help promote adhesion on subsequent layers. Then I would lay down two wet coats, let it dry, rub it out with 1000 grit wet/dry paper, then two or three additional wet coats. Once that was dry, I'd attack any orange peel with 800 grit (very lightly), then 1000, 1500, and when I could get my hands on it, 2000 grit (hard to find in my area). Then buff it with rubbing compound, then scratch remover, and finally a really nice polish cream. That would bring out that smooth mirror-like finish, and I believe the process is pretty similar when using the 2 part automotive clears. You just can't rush it, if you want to get it right, and even with a buffer, get ready to sweat. buffing it out to that shine takes time and effort.
Agree with forever young, a lot of the work is in the cutting and polishing. Also, you need to stick to the recommended time between coats religiously to avoid crazing as it dries, and keep a consistant temperature to avoid blooming (clear will get a cloudy look).
I have been painting cars for years but am just now getting into airbrushing... There are many different brands of automotive clear coats out there and also many levels of quality. If your work isnt going to be exposed to sunlight regularly an intermediant quality clear coat should work well for you. The brand 'Finish One' is available here in Arkansas at automotive paint stores for between $80 and $100 a gallon including activator. Mix 4 parts clear to 1 part activator and apply two full wet coats. Wet sanding with 1500 grit to remove texture and buffing will yield an incredible finish that will blow you away! With practice and a good paint gun you can really lay down some clear coat that will probably not require any buffing at all. However, if I was painting a guitar or a really nice car....no one can lay down clear like a wet sanded and buffed surface that has been done correctly. I hope this helps.