I've bedded quite a few actions and barrels, but never a muzzleloader.
If I did, I'd go with the old tried-and-true rifle bedding materials kits: Accraglas, Mile & Gilbert "Bedrock", or Brownells'. All are available through Muzzleloader Builders' Supply, Track, or Brownells'.
All those bedding kits contain virtually everything you'd need: release agent, bedding material, coloring agents, etc.