ORIGINAL: buzzard bait
Regarding Konrad's question, modern dope is apparently entirely compatible with old dope, nitrate or butyrate. At least, I have patched up 35 year-old airplanes using modern dope. The thinners used may vary since they have several components. I've been using dope a long time without noticing any change or problems. If the plane is old enough you can even put nitrate on top of butyrate, which I have done. I think nitrate sticks a little better, so that's what I put down first, then the butyrate.
I think what you are referring to is Aero Gloss, which was different from other dopes and got reformulated at some point. Maybe others can comment on that.
Jim
Good to hear that you have been able to use the new stuff over the old stuff. No Aero Gloss is another material all together different. The formulation issue might have to do with Stits.