The heat generated by black powder is high enough to melt the plastic type wads leaving a mess in your bore. Stick to the paper and fiber wads. If you are shooting at the range you can use some dishsoap for lube on your cushion wad. For hunting you might want a more stable lube that won't bleed into your powder charge. Circle Fly (or whoever is making them now) has the wads you need until you figure out how to make your own cheaper. Safety is very important. This is somewhat different from managing a single barrel muzzleloader. And it is easy to get shot load moved forward off the charge while hunting, and you don't want to be working over an empty barrel with the one next to it loaded and capped. That is why I suggest you get with a qualified instructor to learn the shotgun procedures to keep you whole.
