A bore brushed, soapy water bucket-bath should remove all traces of bore butter. Doing the same bathing procedure with a ramrod jag, instead of a bore brush, will not be as effective in removal.

Best remedy?..... ditch the Bore Butter and clean/oil your muzzleloaders like you would your centerfire rifles. Run two patches of 90% alcohol to rid the bore of oils, before shooting it again at the range.

If hunting up-north, I use one of two products that have a small amount of bore preservative in it to swab.
That way the gun will never show signs of rust, shooting it 1-2 a day for an entire week of hunting. Always follow the wet swab with both sides of two dry patches.Breechplug should be open when swabbing, with no spent 209 primer in the breechplug face.

1) Birchwood Casey 2 In 1 Bore Scrubber/Cleaner
2) Butch's Blackpowder Bore Shine.