If you make the paper cartridges so that they taper, they will be easier to load, and they will split when the ball is compressed. If you are using a hot enough cap, you can pretty well dispense with the nipple pick.
I also dip the ball end of my cartridges in melted bees wax. This puts some lube on the ball, and it helps seal the cartridge to the ball.
Transportation can be a problem as well. If you cut strips of kitchen foil and use them to wrap a cylinder's worth of cartridges, you end up with a very sturdy little packet that can be carried in a shirt pocket or dropped in a pouch.