Ursan: You need to play with your gun until you get the least- orange peel possible. Thinning about 10% sounds right as long as it comes out of the gun pretty well.
It is a good idea to sand your primer using a hard block and sand it until it is FLAT with no texture to it. A final sanding with 400 grit is great to ensure there are no scratches showing up in your color coat.
As for buffing a single-action buffer with a wool pad (I'm kindof assuming that single action is the same as a rotary) and some coarse compound (in the real auto-paint world we use Meguiars M105 or the consumer grade product- ultimate compound) after a good wetsanding with 1500 and then 2000 grit sandpaper works very well. You'll get even better shine if you follow this with a DA polisher and some fine polishing compound (such as Meguiars m205 or scratch-x) and a softer pad. This will remove any swirl marks from your rotary. A final coat of wax and you're all set.

Since you have all this equipment, it is kindof a bummer you didn't simply spray catalyzed automotive urethane. It would have cost you about the same (~300 dollars for primer and color coat with all the activators and reducers) and probably lasted you much longer. Well anyway, good luck with the rest of your paintjob.