Kootne and Willis both offered the best advise here. Wads are problematic in any blank cartridge fired in a dedicated blank gun. Having made both "theatrical" blanks for stage-plays and reenactor blanks, I would use about 10 grains of FFFg black powder then fill the case to the mouth with cream of wheat (semolina) cereal. I would then compress the load and refill with more cream of wheat until the case was full and compressed hard. As long as these are not subjected to a lot of rough handling they are fine as is and won't create dangerous fragments past 10 feet. If I am storing them for a future event or carrying them in a pocket, I melt some bee's wax and brush a very thin coating over the exposed charge. These are quite loud in a small blank gun but do require cleaning after firing.