Larry,
Solortex is magic covering. You dont need nothing. No primers, no sanding or scuffing, just paint. We/I have used solartex on everything from my Power Slope Scale gliders, to Top Flite 60 size warbirds. I used it exclusively on my built up flight control surfaces. I do recommend using the natural or white if you are going to paint over it, just have the paint not be tinted. There was one issue we had with it. We wanted to show a cloth like texture on a cub, but once the paint laid down, the weave went away. Gave a very smooth finish. We have used all types as well, it will take it all, and alone it is glow fuel proof.

Enjoy it, I cant find it anymore around here.

Ray