If you ask any of your experts in the airlines engineering maintenance department, they will tell you something that has been well-known since Man first starting sending little lead balls down tubes - lead is self-lubricating, and little balls of the stuff require nothing to help them on their way down a highly-polished steel barrel.
The purpose of slopping grease over the end of the chamber is either to give some degree of comfort for those who STILL believe that a flame can ooze past a sealed in chamber ball, or to keep the fouling soft.
Take your pick.
On the other hand, if you don't believe ME, post your comment on www.muzzleloadingforum. com, where any five shooters taken at random have over 200 years of BP experience, and see what THEY have to say. Although I've been a poster there myself for the last twelve years, I promise not to stick my $0.02 in.
tac