You can use butyrate dope. Butyrate can go over nitrate but not vice versa. Kind of like putting lacquer over enamel nitrate over butyrate is a no no but it sounds like the Coverite finish is Nitrate based. I've always used the plain coverite and put dope on top of it. Like in full scale the bare fabric needs to have a few thinned out coats of Nitrate before the Butyrate is used because Butyrate does not bond as well to the raw dacron fabric. Sorry if I rambled on.