For a .36 caliber you would need a .350 to .345 dia round ball.
Mostly you're going to find .350 diameter balls. With a 350 RB. You'll need to run a pure cotton or flax fiber patch in the range of .012 to .015 thickness up to .018 but that would be getting hard to load. Depending on your barrel rifling dia is cut. Your ball plus the thickness of patch should be just over the rifling dia by .002-.005
After shooting find a shot patch it should be frayed at the edges but no burn holes or cuts. If its burned a bit in the center that's ok, if on the edges you'll need a thicker patch. If its cut the riffling or the crown is to sharp and cutting the patch.
Im pretty new at the flintlocks but from very experienced builder that got me started told me. Good luck