While I haven't used Pactra (Aerogloss) dope since about 1960, I'd stay well away from it. From what I have read over the years, there were two or three different formulations, which may or may not be compatible with anything else, including earlier or later Aerogloss. Nobody seems to know for sure what to use for thinning.
There was a discussion here on SH, of old AG within the last two weeks. The general concensus was to avoid it like the plague. Or, in my case, Tetnus shots...I had one almost a week and a half ago, and I swear I'll never get another one. Right arm still feels like it's been shot with a .30-30.

Steve