Always clear over graphics
All airbrush paints do not have UV protection chemicals. They must be cleared with a top coat clear for Ultraviolet sun ray protection. House of color SG100 is an intermediate clear coat to lock down your graphics to allow U to sand down any edge and pin stripe with enamels. It's cheaper than a top coat clear, as in it does not require the hardner. hardners are expensive. It does require the reducer.
This allows U to clear with SG100, 2 coats, sand 800 or scuff with 3M Scotchbrite Ultrafine Grey pad in 30 mins., 2 coats color sand or 3M Scotchbrite Ultrafine grey pad and top coat.
If U sand with sandpaper ease up when U are close to finishing, U can change the grit of your paper just by the pressure U use. If U are still using clogging sandpaper up to 2000 grit sorry we lost UR soul. 3M makes Schotchbrite pads that equal 2000. They last ten times longer and never clog. Always sand in one direction especially when near the top coat. Well how can I do that on a helmet? sand around the edges, rivets first and then one direction.