I use the same wads (cut from old milk cartons or poster board) over the powder & shot.
ffg powder, 2 wads, shot, 1 wad.
Just be sure the 2 wads are firmly seated on the powder. I like to start them together to avoid trapped air between them.
You can also use a pin/needle to make a small hole in the over shot wad to be sure it seats firmly on the shot.
