Hi mate. I used mixture of 50/50 duratec high gloss and white gelcoat. Mixed them two and then added mekp at 1.5%. My gun is 3mm spray tip 1.5hp dewolt 15 gallon compressor with oil water filter.
I suggest if you go with gelcoat then pick a day with temperature between 73-79 degrees sunny no wind. In high temps over 80 gelcoat kicks off too fast. Once you done leave it along for 24 hours then wet sand and buff all the little imperfections.
To finish I used 600 grit then 1000 then 1500 then 2000 all wet sand soap and water. Then aquabuff 2000 at 2500rpm and finnal polish was 3M finesse it. Came out amazing showroom finish. I haven’t polished it all the away because I still going to build top cap so there will be fiberglass joint to the hull that would need to faired before paint so I will do final buff when all done.
If I do it again I would mix deratec at 30/70 (drura/gel) first few coats then final coat I would shoot at 50/50.
Hope it helps. Let me know if you have anymore questions
Ps: all best finish is in your prep. The more time you spend on prepping ie fairing sanding then better it will look after spraying.