I would like to order the frame sealer for the under carriage of my 85' suburban. Will 50 square feet be enough for the axles, frame and differential covers? and will i be able to paint over certain spots with the color I want in certain areas?
That's alot of area for the quart of RustSeal to cover. You'll probably need an additional pint/quart to apply the recommended two coats.
As for painting over, sure just apply either a primer or your desired topcoat after RustSeal cures at least 2 hrs and before it completely cures (about 8 hrs) and that paint will stick great.