I second the petroleum jelly/beeswax blend for all BP shooting. Simply adjust the ratio for the weather. More beeswax for hotter seasons, more PJ for colder days.
Some use a lard based over ball lube or something like crisco. I don’t know how hot it is where you are - Winter, right? - but if I tried only petroleum jelly or shortening this time of year, it would be melting down the front of my cylinder!

As for the powder charge, I would simply fill a chamber up to .454” below the cylinder mouth expecting the powder and ball column to be roughly flush with the cylinder mouth and then a little below after pushing the ball home compressing the powder and leaving enough space on top for your smear of lube.
I don’t think you need all that much lube for a pistol.