I use them all the time. I made a cylindrical wood dowel that I use to form the cartridge, I lick the paper and wrap it around the dowel and then crimp the end and put a dab of white glue to hold it. I make about 30 or so while I am watching TV.
With the paper in a cylindrical tube, I measure out 25 grn of holy black and put it in the cylinder and then place a ball on top and with my fingers I twist the top tight against the ball, fold it over and glue the end down so it will not open.
So now I have a paper cartridge that is ready to go. Some people talk about nitrating the cartridge to make it burn better but don't worry about that it will light no problem.
So when I get to the bench I put a complete paper cartridge into a cylinder, rotate it to the seating position and ram it home. Then I proceed to load the other cylinders.
I take a small brass pin and just to make sure the paper broke inside the cylinder when it was rammed home, I push thru the open nipple into the cylinder on each one that is loaded. Probably don't need to do that but I have never had a miss fire so I do what I am used too.
I use some bore butter on the balls, cap each nipple and away I go.
If I am going to be shooting conical bullets then I make the same cylinder paper cartridges but I just load them with black powder and that is it. The conical bullets are already lubed and sitting in a tin box so when I am at the bench I simply drop a paper cartridge into each cylinder then ram home a conical on top, make sure each paper cartridge is broken in the cylinder by pushing the brass needle into the nipples, cap it and away I go.
Might sound like a lot of work but honestly you can load each cylinder in under a minute, rotate the cylinder and poke thru the nipples in under 10 seconds, cap it and away you go with a total time of about 2 minutes max.