Villiers, are you still working up loads for the Werder carbine or is this for another rifle?
I don't know if Lee Liquid Alox is available in Germany, but it seems to add stickiness to beeswax. Probably doesn't need to be 50/50 as is common for smokeless loads, and traditionally some sort of softer lube is used for BP, adding lard or shortening might help. Even Vaseline/mineral jelly, maybe? Beeswax doesn't seem to stick well until it's completely cooled, but applying it i the cooled state doesn't do well either. Either tuble coat the bullets or do the cookie cutter trick after letting the mix cool all the way. The lubesizer might be problematic with your odd size projectiles, unless you can get one bored out to the desired diameter.