My only experience with blank charges has been during parades, where we shoot off blanks to please the crowds. The first year, I pre-measured loads into tube I made from some orange Stationary my sister had sent to me years before. I poured the powder down the barrel, and then ramed the paper down on top to add compression, so that the sound would be louder. It was, but I also created "Orange Confetti", that some in the crowd likes as it rained down on them, and others didn't. Occasionally a piece of paper would be burning when it left the barrel, but it always burned out before it came close to the ground or to endangering people.
The next year, I poured plain BP down the barrel- a lot more of it, so that the weight of the powder contributed to the compression --- and skipped the paper tubes. No more fire hazard! I was using 120-150 grains of FFg powder in my .50 caliber gun, and it roared like a lion- a sure crowd pleaser. Lots of fire out the muzzle, lots of smoke, and a lot of unburned powder that burned in the air , or fell to the ground with a quiet "patter".
If you are going to be a re-enactor, follow their rules.
The second year my club did parades, we made a rule that forbade ramrods being used, or even carried in the guns. They could be carried in our club covered wagon, but not in the guns. Every participant's bag was checked to make sure he was not carrying any lead balls, either. And short starters were left behind, too. We burned up a lot of powder- I went through almost two horns of powder in one parade, but the crowd loved it, and cleaning involved the same amount of time. The water does that job.