Just a "trick" to use when hand painting
Get some " Owatrol Oil" add 10 -15% to the gloss coats , this will retard the paint hardening slightly, then roller the paint on using a "radiator 6" foam roller" horizontally on the panels then draw the paint off downwards or at 90 degs using a good dry brush
This will get a good smooth finish, I have used this method on Trucks, Boats and Vehicles for a number of years and gives a good relatively brush line free finish
Baldy