MG Chemical makes a similar product. It also come in a spray can.
Here is a version that you brush on.
https://www.amazon.com/MG-Chemicals-..._&dpSrc=detail
The aquadag falling off the CRTS of RCA sets of that era is common, I've got one or two sets with that problem.
Thermistors frequently go bad. The fact that your's is unplugged might mean there is other problems.