Hi

Although not with Koverall but when I have sanded thru the KK primer to balsa over fiberglass cloth I carefully applied a very small amount of thin CA using the small tubes to stiffen up the surface and sprayed on a light coat of the KK Primer over it. Then lightly sanded with 320 paper before final paint.

You might try applying a very small about of the KK Primer with a small brush to "stiffen up" the fabric and then ever so lightly sand it to blend it in.

As to a primer over a Koverall/ nitrate Dope surface as well as natural Solartex/Nitrate have used F&M St*ts Polyspray with excellent success over a fabric surface. Then applied the KK paint directly to the PolySpray. The Polyspray helps fill any small bumps on leading/trailing edges with almost no weight and sands ever so easily..

Cheers
Ray