Pulverone sometimes refered as granulated, is ball milled black powder that has been slightly moistened so that it just clings together and pressed through a fine screen (a window screen will work). The resultant granules are dried and used for a number of different tasks. While you can leave the black powder in the ball milled state for packing in tubes - it will be a fine dust and very hard to work with. Making pulverone out of it decreases the dust problem and actually makes the hotter powders useful as lift powders because of the air spaces between the grains.
Sieve the black powder to remove the milling media and wet the composition with alcohol solution. Mixed until you get a nice thick solid paste (consistency of play dough or when you squeeze an amount in your hand it sticks together), try not to get your mix too wet or it will become gooey and useless. The trick is to add a little solution at a time until you reach the desired consistency. If you do make your mix too wet simply add more meal powder and mix together again until you reach the correct consistency. Take your paste and press through a mesh screen to granulate. Spread the granulations out onto a newspaper to aid in the drying process and place in the sun or similar for a few days. The resulting dried granulations of black powder is called pulverone.
Adding dextrin will slow down the burn speed of black powder (although very minor) so you may want to experiment with different amounts you add depending on your intended purpose. You can also use different sized mesh screens to achieve various grain sizes.