This may be true of Pyrodex; I don't know as I've never used any. If you use Hodgdon Triple 7 you do not need hot water. Triple 7 is hydroscopic but non-corrosive, and the residue dissolves in cold water immediately. My cleaning procedure is to run one patch dampened with tap water, followed by a dry patch. I then repeat, and the second wet patch comes out clean. This patch is then used to clean the exterior of the firearm. A wipe down with T/C Bore Butter completes the cleaning. Many years of completely rust-free use have proven this procedure.