Several years ago, when Hamilton Bowen was trying build a "modern" version of the rare old British .577 revolvers (and who but he could/would do that "just for grins" ?) and was having trouble putting consistent, accurate BP ammo together for the project, he asked Mike Venturino for his advice.
He stated that IHE loading BP cartridges for both rifles and handguns, he always uses a drop tube to charge the cases. The resulting loads have proven to his satisfaction to be enough more consistent, accurate and deposit less fouling to be worth the extra trouble.
He recommends the use of Magnum primers in both. Ignition is said to be markedly better resulting in more efficient burning of the charges, consistently better accuracy and less fouling.
He uses very "soft" alloy for all his bullets: no more than 1/20 tin-to-lead, IIRC. He also prefers bullet designs with ample lube grooves and using BP-specific products in them. "SPG" and Lyman's "Black Powder Gold" were mentioned specifically.
He also recommended always using a vegetable fiber wad between the charge and the projectile.
Mr. Bowen reported in his article that once he'd followed these principles while putting ammo together for his project his revolver began to shoot much smaller, much more consistent groups and that many more rounds could be fired before functional issues due to fouling build-up began to occur.
I very seldom load BP or Pryodex in anything other than C&B revolvers or my single muzzleloader, but when two fellas with experience and credentials like theirs speak on a subject, I tend to lend an attentive ear to their opinions. Just my $0.02.