YOu can't Oil or grease a paper tube without it contaminating the powder, eventually.
Some shooters dip the ball end of the " cartridge " into melted beeswax, or parafin wax, and then let it cool. The wax serves as a bore lubricant. ( Bore butter, for instance, is half wax, and about half oil. Wax is a common additive to patch lubes.)
You would be much better off using Jim Rackham's system in your fowler. Using ONLY OS cards, which he pokes with an awl to give each card an off-center hole that allows air to pass through the card, use 4 cards over the powder, and 2 over your shot. He puts a ball of waxy lube between the 3rd and 4th cards on top of the powder charge, and lets the lube be squeezed between the two cards to grease the barrel as the gun is fired. The cards allow you to use these in barrels that have chokes at the muzzle, because the thin cards can be bent slightly to fit through the chokes, before being turned and seated down the barrel. Protecting the edges of the wads is what makes wads do their job. Put the 4 wads in so that the holes DON't Line up. I purposely set the holes at 12,3,6,&9 O'clock positions at the muzzle as they are passed into the barrel. The two cards on top of the shot have their holes set at 12&6 o'clock. The holes do let the air pass out from behind the cards, so that the air does not break an edge instead. The thin cards weigh so little that they quickly fall away from the line of fire, whether shooting shot, or PRBs. Jim posted pictures of his excellent patterns using OS cards, and one picture of a typical pattern he got using the more traditional wad combinations( we all have used). The OS Card patterns were noticeably better patterns.
Of course, you have to test these things in your own gun. I found, for instance, that my 20 gauge fowler is actually a 19 gauge fowler! I only got it to shoot at all when I bought larger diameter cards.
My gunmaker was shocked at what I found, as he ordered my barrel from the same supplier as had provided him a barrel for his own fowler. We pulled that gun off his gunrack and measured the barrel, and it came in at .615" the correct dimension for a 20 gauge barrel. Mine is .626! I took my gun to his shop just so he could measure it with his own calipers, rather than trusting my measurements. Circle Fly makes wads and cards in just about every gauge, so getting the 19 gauge OS cards( and some OP wads to use with PRB) was not all that difficult.