I heard Melted wax and cut shells do work.
I’d want to try a cut shell first. Because the wax/glue residue can and will build up in the barrel.
Not that I’ve ever used such things. ‘heard they might be ‘llegal.....
I think it was Taofledermous who has all kinds of shotgun shell videos who showed how wax can melt depending on the outside temperature. I think the Elmer's glue did fine and left no buildup as it all went out the barrel.