Sealing Dynomax headers

I have been having problems getting these to seal in the past. The engine is going back together on Saturday on the 75 dart and I wanted to finally fix the problem.

I have heard that you can use permatex, but is it in addition to the gaskets or in place of the gaskets?

Do you let it set up a little?

What kind exactly do you use? Red, Black, Blue or other?