Help freeze plugs and cam plug leaking

I wouldn't use shellac, regardless of who recommends it. See that description? "Economical sealant". When I am sealing something, cost is the last thing I look for. Silicone RTV will go into small holes and imperfections and seal very well. It's thick. Shellac is very thin. I've sealed some freeze plug holes that probably should have been bored over size because of pits in the circumference of the hole and without gooping it on too thick. The stuff just works. That's exactly what it's made for. That Indian Head stuff is a trip back to the 1940s. The only other product I also like with freeze plugs is Permatex #2. It also works very well. It has a pretty high maximum operating temperature, 400*. The high temp red RTV is still higher at 650*. The Indian Head shellac is only 350*.