Plumbers tape is more like tape, whereas RTV gasket seal comes out of the container like a gel, but when it dries, it turns into like a soft rubber. Gasket seal is very, very easy to just peel off once you don't want it there anymore. I used to use this stuff in automotive applications on parts that would end up very hot, so the heat of a barrel may not be much of an issue. I haven't ever tried it for this specific purpose, but I believe it may work well here.
It is cheap, available, and even in the smallest container should last for many applications as I don't believe it would take much to keep the thread protector in place if it is tightened down after an application. It would be what I tried first if I saw this as an issue.