Every day a little paint

Lately I seem to be trending putty failure that turns out to be paint failure. A few estimates I've been on lately seem to have what looks like chipped glazing but is in fact the paint separating from the glazing putty. In my experience, the glazing companies are not exactly forthcoming about what "top coating" to apply to their products. Sarco recommends oil primer over their glazing but when asked "what about if I'm doing a shellac/varnish finish with no paint?" they have no answer except to use an oil primer. I guess if I were painting windows I would use oil primer as a default. My guess is no one has told the painting companies this recommendation.