yes , I think it can be made in another way, he had a lot of time obviously.
the reloading press is the right tool to press the pellets. when they made such cartridges in factorys the powder was pressed in a die and than eject from the die the next moment. they had no time and tools to let them dry for 24 -48 hours there. using dextrin and water to bind the blackpowder looks like the very best way to me. its cheap and ecofriendly, allways good to have some water in the mixture if you work with blackpowder.
I would try to get a bullet with a pivot at the base or a hollow base to press the blackpowder pellet together with the bullet in one process.