I have never used anything. Just bolted them up and called it good. I always used the one I took off my car and I don't know if that helps, or not. The factory did not use one.
If you want to use something, you could try about 1/16" layer of red high temp. Smooth it out nice and even, let it set about 30 minutes and then bolt it on. Let it set overnight and pray like heck that if you need to take it off again, that it will let go and come off. Setting for the 30 minutes should make it less gluey.