they will blast off or severely rough up the chrome (i think). because chrome is so hard, they will probably have to use a hard media as well. i'm no expert.

you probably don't even need to fill the pits if you are painting. i've never used it, but you can probably use bondo for pits/dents if you want. you can probably get a smooth surface just by sanding.

paint primer is forgiving and will fill in a lot of the small pits. if you are getting it professionally done, they will probably prepare it well.