Yes 1/8 " pin striping is what the 501st calls for.
Prime your helmet then sand smooth with 400 grit then 600 or 800 grit sand paper. I use the wet sand paper.
It can be painted however you want but keep the following things in mind. Paint will not stick well and shows lots of fish eyes when applied over Rub N Buff, pin stripping might not stick to RNB either. It's easier to paint a dark color over a light color.
Also Boba and Jango helmets look similar at first but are in fact very different when compared to each other.