Do I have a bad head gasket?

Well just turning the engine by hand I could see air bubbles coming up through the radiator. Pulled the heads and nothing stands out but I still think it's the problem. I figure if it's not bad enough to have fluids mix it may not be bad enough to see by eye. So new cometic gaskets are on the way and also some new trick flow heads. I wanted to upgrade to them this upcoming winter and figured now would be a good time. What type of sealant do you spray the head gaskets with? I can't recall what it's called.