Anti-rust or anti-seize, I'm not sure where you saw rust!
I use a Loctite product. "Hi-Temp Anti-seize Compound with Nickel".
I apply it to the seat and the threads.
As stated before I apply silicone lub to the porcelan portion of the plugs to provide ease of removal of the plug cable.
An anti-rust won't withstand the high temperature the threads of the plugs experience. I would imagine that would be no higher than 200 degrees F. Considerring the rubber insulators don't carbonize except with time and temp and you can hold the plug bare handed. I just never considered the temp before.
Possibly some else could elaborate on the temp.
Good Luck oliver and ymsim.
Happy Trails Pip Pip from Houston!!!
Donald, El Cheapo, Yank
Book Number Three