I have the exact qt can in the shop somewhere. I have not seen it at stores for years.
In the late 60s at a tire store that did it's own recapping, they had some stuff that was concentrated and mixed with gas
I don't recall the brand or even the container
I"ve heard the word "china black" as a very "coverall product", but have no clue if you could add it to something that would coat a tire.