if you've never loaded a BP revolver you need to have somebody show you how to do that. mostly i play with rock locks, but my mom has told me how exciting a chain fire in a revolver can be. you need to load each cylinder and grease around the ball so the flash of firing doesn't set off the powder for the cylinders that are not lined up to fire, and be sure to leave an empty cylinder for under the hammer.
mostly i have preferred real black powder to the substitutes, and in a pistol i would think that some 3f would be the best choice. go to a reloading store, if they don't have it on the shelf in back they will be able to get it for you. be sure to tell them it is for a BP gun and shooting. my local Graff Bros. always asks, using it for pre 1898 guns or repro's is a specific exclusion for BP to be purchased by non licensed individuals. BP is an explosive and the other substitutes are non explosive.
have fun . be safe