I changed to a sanding disk and smoothed out a lot of the really rough spots.
I probably don't need to mention the potential health risks when sanding fiberglass...
none the less, I used painter's plastic the isolate an area in my workshop and used head-to-toe Tyvex cover-alls, latex gloves, a bandanna and, of course, a respirator.
When the flat-black was dry I used a foam paint roller to apply some slightly tinted, flat-white enamel paint. I tinted the white paint with some brownish-yellow paint that I got for $1 in the 'oops' paint at Lowe's.