Alox with real BP, very, very BAD idea. It combines with the fouling to make it way harder to clean.
Back to powder coating, I've experimented with it in both modern cartridge guns and muzzleloaders. In regards to the fouling, it does nothing to lessen or soften the fouling. Softening the fouling is a function of the lube and kind of BP. It can help with guns that have leading issues due to pits in the bore. In my guns, both muzzleloaders and cartridge, there were very mixed results in regards to accuracy. Most didn't change much at all. Two shot worse, only one shot better. In the one where it shot better, 1858 Smith, I can only attribute it to the coating bumping up the diameter of the bullet as this bullet is a tad undersized for my bore.
I think you chief benefits in powder coating are reducing leading and allowing for somewhat higher velocities with smokeless powder. The technique does work, just not in every case.