If your bumpers are down to bare plastic, smooth them over with some 500-600grit, use a plastic adhesive promoter like Bull dog( spray can)then primer( you can also get some plastic cleaner if it's in your budget to wipe off beforehand).2-3 coats of primer.
Wet sand primer with 500-600 wet/dry and red scuff in the crevasses and edges.
For a decent budget paint use nasson or similar brand base and clear.more costly brands you can get spies hecker, sherwin Williams, ppg, and dupont( Nasson is duponts "cheaper" brand),but all the brands above have a cheaper brand also.
Keep in mind red paint is usually higher. You can also look at single stage for slightly cheaper.
2-4 coats of base and 2 coats of clear.
All this assuming you have the equiptment to do it, like air compressor and spray guns.
Hope this helps, good luck!