I strongly support the suggestion to use cold water.
Also the comments on Swiss powders.
I run Goex and Swiss in my rifles, most of them prefer the Goex, and they all seem to agree (over the chronograph) that "F for F" the Swiss 'Fs' are hotter.

Regardless of Swiss or Goex, the genuine black powder is the easiest to clean up of all powders, the only solvent needed is plain old water, and you can wash your mops and patches then re-use them if you wish...

Cheers
Tinker