Jim uses flexible fibreglass for his armour parts, which is just as easy to work with as ABS.
It's a good bit thicker & as the name says, quite flexable, which is very handy.
There's also little or no prep work, other than a light sanding to remove any dust prior to the primer coat. From memory, I gave the armour 1 coat of primer & two coats of paint with 1 or two coats of varnish, with a little light sanding btween coats.