I take all the twist out of my staves.
Here are a few tips;
I use a piece of aluminum angle as a reflector for my heat gun. I get a more even heat distribution and can heat an area in a third the time. After I heat an area I wrap a rag around it and the reflector to hold the heat and let it penetrate deeper. The reflector will really hold the heat so keeping it close to the stave is like putting the stave on a low temperature stove eye.
I remove twist like George but us a pipe wrench and a 5 gal bucket to add weight to. I have 2, 25# bags of lead shot I put in the bucket plus an assortment of C clamps if I need more weight.
I have found if I put a piece of old sanding belt around my stave (rough side in) the pipe wrench won't slip or chew up the stave.
