I have been using it for 25 years. When I first started out I did not understand it ...chemically speaking. Are you using Gloss or semi-gloss?
http://www.van-dee.com/index.html 1) Spray guns are like footwear. You get what you pay for... Ex: Walmart shoes wear out in 3 weeks and the vinyl craks in heat, Florsheim shoes last nearly forever.
Devillbis, Thayer & Chandler are the best money can buy, the ones at Walmart, Home depot, Lowes... "Cambell Hausfield" are crap. Middle of the road guns can be found online, Google... "Paint, HVLP spray gun, body shop supply".
2)I usually spray 6-8 bows at one time so my Fullerplast is mixed 16-1.. I use 24 oz. pickle jars to measure the mix. 16 oz. of fullerplast and 1 oz. of part B catalyst.
If I have a small batch say..2-3 bows 8oZ Fuller to 1/2 oz. of catalyst as far as thinner, use medium drying laquer thinner and pour perhaps a dixie cup of thinner in the mix or half that. the mix should be perfect when you stir it, dip a CLEAN screw driver in it and when you draw the screwdriver outr the clear should flow nicley off it like thick water.
3) PSI is 35-40 lbs. make sure you have clean air lines.
4) spray EVEN coats at 12" distance to the bow...back and forth, left to right or up and down taking your finger off the trigger at each end.
5) 3 coats first, wet sand, then 3 more wet sand..etc. etc...treat the bow like it is a 1963 Corvette. decide what you want it to look like and set your expectations at that point.