I think it's more a matter of damping than tamping toward the end. The problem is harder to deal with when you smoke a large pipe than a medium or small bowl pipe. If a dottle tastes really awful and I can't get it to burn, I dump it, and probably will avoid buying any more of that particular tobacco -- or maybe stop smoking that pipe if the problem is persistent. Sometimes, I will mix PA or something with a recalcitrant mixture, so that it doesn't create a nasty dottle to begin with.
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