In the Civil War, both sides used paper cartridges for their revolvers.
This was a paper tube, filled, with powder, with the bullet glued to one end and the other end folded over or rolled to a point to keep the powder from falling out.
So, you simply had to place a paper cartridge in the chamber and ram it down. Then place a cap on each nipple.
Far faster than using a powder flask.
As the owner of five cap and ball revolvers, I'd guess that paper cartridges could be rammed into a chamber in 5 to 10 seconds each. So, you're looking at 30 seconds to 1 minute to reload.
Then, you have to place those itty-bitty caps on each nipple. I give that about 5 seconds per cap.
So, figure about a minute to 90 seconds to reload a cap and ball revolver during the heat of battle.
Some soldiers carried extra, pre-loaded cylinders. The empty cylinder could be removed quickly from the revolver and a fresh, loaded one substituted.
This was even faster but dangerous.
A capped cylinder loaded with powder and ball rolling around in your pocket is not a conducive to long life. A sharp blow from the cylinder hitting something else in your pocket, or your pocket striking an outside object, could fire a ball into your leg.
These were the days when anesthetic was new and antibiotics were unknown. What might be a minor wound today could be fatal back then, especially if it became infected.
Though the paper cartridges were faster than a powder flask, they were more fragile and susceptible to moisture.
I've heard that some soldiers preferred carrying a powder flask for this reason but I find that a bit hard to believe.
Colt, in particular, went to great pains to create packaging for its paper cartridges that was particularly sturdy and moisture resistant.
Colt would take a small rectangular block of wood, slightly larger than the diameter of the cartridge. A line of five or six holes (depending on the caliber and model of the revolver) were bored along one edge, but not all the way through.
Then the block was split lengthwise, creating two halves with half-holes, much like a bullet mould.
The block was placed back together, the paper cartridges placed in the holes, then a length of string run around the long edge of the block. The block was then wrapped in heavily-waxed paper, leaving the tail of the string exposed.
In use, you pulled the string around the edge of the block, tearing the waxed paper as wel. This "split" the block again, exposing the cartridges for easy handling.
I am uncertain how soldiers carried percussion caps for their revolvers. I can't imagine fiddling around with that small tin during the heat of battle. They must have carried the caps loose, in a tight-fitting pouch, on their belt for quick retrieval.
Colt also used stiff paper boxes to hold paper cartridges, wrapped in heavily-waxed paper.
Samuel Colt pioneered the use of paper cartridges in his revolvers. His first cartridges were made of tinfoil, not paper. He had to order the foil from Germany; American foil was not of sufficient quality.
For some reason, probably expense, he stopped using foil and went to nitrated paper cartridges.