With Bismuth, you don't have to protect the bore. With iron or tungsten shot, you will have to "likely" use steel shot wads. That is what I would do.
Steel shot wads are thicker than lead shot wads, as the thicker material is needed to protect the bore from the hard shot.
Powder, then over-powder 1/8" hard card wad, then shot-cup, then the shot, then the thin overshot wad.
I suppose you could make up a ctg. but steel shot wads might be too large in diameter to be encased in a paper wrap.