First off the bat you have to figure out exactly what size the bore is. You said it smaller than .24 gauge/.58 cal., maybe it is .28 gauge/55 cal. or something in between?
I know a lot of guys here like wad punches, but I much prefer a nicely Re ground hole saw of the proper size with the center bit removed. One of these babies in a drill press will turn a moth eaten chunk of old wool army blanket into wads ready for grease in no time flat.
I think once you get this wad thing sorted out, you are going to be pleasantly surprised at how flat you little smoothbore shoots, and how tight the pattern is. Just remember that with small bore trade guns, or fowlers, the shot string will be long. So you will have to increase your leed on wingshots. Good luck.
Hungry Horse