black powder shotgun ordered...

[Rustywreck]

This gun is choked, in fact I ordered an extra X-full so I can have both barrels full choke.
I've read some about making loads with a shotgun. I do remember in one of them the cautioned about using standard shot cups, as they are smaller than the size of the bore (due to having to fit in the shell).
I haven't been to my favorite gun store to see what they have for wads of the correct size, but I'm guessing it will minimal since blackpowder shotguns aren't very popular - a few of my friends are asking me, "what the heck are you thinking?"
I do have a couple books on black powder shooting, but didn't even think to look at them.
I read about using cardboard of different thicknesses for the over powder wad and to hold the shot in place.
For those who use this kinda stuff, is it something I can buy at a place like Office Max and cut to size?