Auto body repair & detailing: Refinish Clearcoat, stage paint, acrylic enamel

Question
Thanks Bill,
I have plenty of clean air flow in my homemade booth. I think the orange peel was caused by lack of atomization.Perhaps not enough air pressure? I'm using a gravity feed devillbiss gun and urethane clear. The gun came with three tips, 1.2, 1.4, 1.7. which should I use on the clear? Also the clear mixes 4 to 1 with hardener, but no reducer on the product data sheet. Should I be using a reducer. Its Martin Senour 3.5 Ultra Gloss Overall Clear Urethane. I'm building a 33 ford 3 Window Coupe and I want to be able to say I did it completely myself, but I also want it Perfect. Again thanks for your help.  Ron
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The text above is a follow-up to ...

-----Question-----
I've got orange peel in the clear which is about 3 weeks old & too hard to wet sand out. It has 3 heavy coats of clear. Can i sand just the clear & recoat? If so what grit paper?
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Yes you can, Ron! Use 600 wet or dry paper, avoid going thru the edges. Anywhere you go thru will have to have the base coat spotted in, or you will see a ring thru the clear. A grey scuff pad will do nicely around door and lid edges, and won't go thru the clear as easily as sandpaper. Always try to buff clear within 48 hours, or it gets too hard. To avoid orange peel, be sure that you have good air flow in the spray area, the correct reducer range, and clear that is rated for overall paint jobs. Be sure your gun is rated for spraying single stage paint. A base coat gun won't put out enough fluid fast enough to produce a nice, wet paint job. You move so slowly that the paint is drying by the time you get to the other side of a panel. (horizontal panels.) It also fills  the air with unnecessary overspray that will come back down and land on the new paint, especially in an area with marginal air flow. If using acrylic enamel be ABSOLUTELY sure to use overall hardner. It will be sorta thick, like cheap waffle suryp. The repair hardner will be watery, and not produce a nice gloss. I'm here if you need any pointers. Bill

Answer
Hey Ron. Urethane clear is an excellent choice. Be sure the hardner is the proper one for your temp range, it sounds like there is no reduction necessarily with your clear, but all clears are adjustable for temperature. If your DeVilbiss gun is an HVLP, use the 1.7 tip, but don't run the fluid wide open. 1.4 isn't enough fluid, 1.7 is probably a bit much but you can always back the fluid screw in. Don't use a cheater valve with an HVLP, either, they rely on air flow as opposed to air pressure. Either use a diaphragm regulator on the wall, or on the gun. I wouldn't be afraid to give it a little more air pressure, either. I think you will find that buffing a show vehicle is just a given, but the better the laying down of clear, the less sanding you will have to do to plain it down. Urethanes are generally a little orange peely. Wet sand the clear to buff with 1500-2000 wet or dry paper, or you can use a D/a sander with 1500 dry. I like the dry method, if the clear cooperates. You can see the peel coming off, and it really buffs down a lot easier than panels sanded by hand. Stop in where you bought the paint, and they will be able to set you up with the proper pad and sandpaper, should you care to try this method. Keep the da slow, and expect to use a pile of paper. Bill