OP, can you tell us what properties you are looking for rather than saying you want to use a specific method? I've had good luck with the 160 degrees "boiling" for larp armor with sno seal. It has held its shape nicely, thickened what I had a little, I was using 8-10oz, but then also didn't become brittle.
But if you want a specific look or property I bet there are a lot of people here who could tell you exactly what you do want to use.