I would sand it and spray it. You could also consider milling off those integral grip panels and drill/tap for grip bushings.
I did a mill/paint/grip job to an early 22/45 frame just like yours. You can see it here
https://www.calguns.net/calgunforum/....php?t=1051014
I have also seen guys dremel those grips flat with a sanding drum then do the bushing mod. You could also leave yours as-is, since they were not painted you wont have to sand them and knock the diamonds of the checkering off.