To make up dummy cartridges that will last, here are some tips based on many years of using my own dummy cartridges in classes:
1. First drill a a set of holes about one sixteenth of an inch in diameter at 90 degrees around the case, put the second set about an eighth or quarter inch away from the first set...you will end up with 4 holes in the cartridge case. These holes help easily identify the cases as dummy rounds.
2. Once you figure out the depth to which you want your bullets seated, fill the rest of the case with epoxy, or lead shot. This helps keep the bullet from being pushed back into the case over time...trust me, this is important if you want to use the dummy rounds long term.
3. After seating the bullet, crimp it as tightly as possible without buckling the case shoulder. A taper crimp works best
If you need to fill the primer pocket, buy a little piece of some nylon or similar plastic, and cut a piece that will just fit the primer pocket.
I strongly recommend AGAINST making up any dummy cartridges without the cross drilled holes as it is far to easy for live rounds to get confused with non-drilled dummy rounds.
If all this seems like too much work, you can buy 'em on line, check out surplus military places as the military uses quite a few...they are usually colored dark brown, black, or something like that.