I've put off surface prep for a while now, because it's so tedious. Finally got it done. I intend to have a high gloss eye blank, to match the high gloss of the vinyl and black painted mesh.
I started with aggressive 220 grit until I got the print lines out. Then I went over it many times with 600 grit to take the scoring down. I cleaned plastic shavings off with pressurized hot water, and dried with a micro fiber towel. With the blanks now very smooth, I used a nice high adhesion 3M masking tape, and cleaned up the edges with an Xacto blade.
Ready for paint!