I like to add a mid bead. Using it as a shotgun, its the same ol' procedure. When "aiming" with a ball, make a figure 8 out of the beads and use the top of the 8 for your point of impact.
I like an unpatched ball that is close to the muzzle diameter. The biggest one that will slide past the muzzle with almost no pressure, and certainly no scraping. Others use a patched ball in smoothbore and have experimented enough to get good results. My best smoothbore ball gun shoots one ragged group at 35-yards. When I move to 50-yards the group opens to as much as 5-inches. A few yards can make a big difference, so you really have to shoot several ranges repeatedly to learn what it can do.