I would respray them. The fiberglass grill on my '97 Aerbus had a lot of chips on it so I decided to respray it a year ago. First I cleaned and sanded it. Then I applied a few coats of adhesion promoter (sanding in between coats), then applied a few coats of primer, applied a few coats of factory color spray paint (sanding in between coats), and then finished it with a few coats of clear coat. I have very happy with the results and it has held up very nicely. Looks like new. I did this over the course of 2 warm days as I wanted to make sure to give it a lot of time in-between coats to dry and cure. Good luck!
'74 F350 44K,'79 11' Mitchell Camper, MINT All Original
'79 Mitchell 25' Class C, 460 46K, MINT All Original
'97 Rexhall Aerbus, 60K, 460, F53, MINT All Original