Your friend can use Black Powder in FFg or FFFg granulations or Pyrodex P or RS powder.
For the .36, the FFFg or Pyrodex P is best as they are finer grained so they develop their pressure faster than the other two.
You should have a powder measure that can be set for 15-30 grains and IMO, something around 20 would be about right.
The others suggested a ball size that will work well. These balls are slightly larger than the chambers in the cylinder so a thin ring of lead will be sheared off when you use the rammer to press them into the cylinder.
This is as it should be. If the balls are too small and don't shear a ring off, they will be loose.
This causes two problems. First, on recoil, the balls in the unfired chambers will move forward which will prevent further cocking of the gun.
Second, a loose ball is likely to contribute to a "chain fire" where more than one chamber fires at the same time.
I agree with the folks who suggest using the Wonder Wads however they aren't really necessary.
What is necessary is to fill the mouth of the chamber with some kind of grease.
The Bore Butter works (unless it's a hot day) or just steal some of your wifes Vegetable shortning like Crisco.
The purpose of this is to provide a positive seal around the ball/cylinder interface to prevent a "chain fire", and to provide some lubrication for the ball when it's fired.
You will need some #11 Percussion Caps.
When placing these on the nipples, they may fit so loosely they tend to fall off. If this looks like it might happen, pinch the mouth of the cap to make it elongated. Then push it fully onto the nipple.
If is absolutely necessary that these fit tightly so that they will remain on the nipple when the adjacent chamber is fired.
When shooting the gun, look at the caps on the unfired chambers to make sure they didn't fall off during recoil.
If one of these caps does fall off, and you fire an adjacent chamber, you will be almost guaranteed to have a chain fire.
When loading, I like to pour the powder into the chamber, place the Wonder Wad onto the mouth of the chamber (if I'm using one), then place the ball onto the chambers mouth.
Then rotating the cylinder so the ball aligns with the ram, I ram the ball down to fully seat on the powder/wad load.
Then I'm ready to load the next chamber using the same proceedure.
After all of the chambers I want to load are loaded, I then install the caps.
Using this method, you will not be working on a partially loaded gun because until you place the caps on the nipple there is almost no way the gun can fire.
There are about 10,000 ways to clean your gun and I'm sure you will read them here, or you can use the "Search" feature the forum has at the top of the page.
The one suggestion I'll make, assuming your shooting an open top Colt design deals with removing the barrel.
First off, the wedge doesn't have to be totally removed from the gun, just driven out so it no longer engages the slot in the cylinder pin.
After doing this, place the gun at "half cock" and rotate the cylinder so the ram will hit the front of it between the chambers. Then use the ram to jack the barrel off of the reciever.
Have fun!
zonie