i would just pour the wax and grease remover on a red scotch brite pad, scrub the roll bar, wipe the bar down again wax and grease 2 times and paint.

in the bodyshop where i work i have wax and grease in a sprayer so i spray it directly on the surface then i would scrub with the scotch brite.

if i were doing this job myself i would spray it with PPG epoxy primer catalyzed with 401 and spray it out with a prevail spray bomb. and then paint with a single stage paint with the prevail spray gun.

****NOTE prevail spray guns are just like spray bombs.
https://preval.com/