Woody,
The first thing you MUST do is get an accurate measurement of the bore size. This can be done with a precision set of dial calipers or perhaps a really good set of digital calipers. If you don't have the means or training, get someone with a machinist/gunsmith background to measure it for you. It REALLY is that important for accurate shooting.
For example, my old Pedersoli Brown Bess Carbine's bore ran .753 inch. The largest ball size then available was a mold that gave a .735 inch ball, leaving .018 inch "Windage" as they called it in the 18th century or what we would call open space in the bore once the ball was inside. I used that ball and a standard ticking material greased patch. I also had to use a big short starter to get the ball started down the bore, but as the patch material crushed down from that, the steel rammer seated the patched ball nicely. The powder I used was FFg Dupont or what is now Goex powder and 70 grains was my accuracy load.
In those days, the mid to late 1970's, the target that required the most accuracy and skill we normally shot at was a double bladed ax sunk into a chunk of log. Two clay pigeons were hung on each side of the exposed axe blade. We shot that offhand at 20 to 25 yards. The idea was you aimed at the middle of the axe blade and the ball would split in two in the blade and BOTH "halves" of the ball had to shatter the clay pigeons on both sides of the axe blade. The load I mentioned above would do that every time, as long as I did not screw up the shot. Using that load and firing offhand, I would hit a one gallon plastic milk jug at 100 yards at least 8 times out of 10. One time for one match, they put a 4 inch long steel buffalo silhouette on the ground at 73 yards and we had to fire at that Offhand as well. Wish I could tell you I hit it, but I missed, though my ball put a divot in the ground only 3-4 inches from the small silhouette. (No one practices for firing offhand at 73 yards that I know.)
Now in recent months, Spence 10 has reported even better accuracy because he uses a shot card over the powder, then a greased wad and finally the patched round ball. Wish I had heard of that back when I was competing with my Bess, as I had the wads and cards to shoot shot in some matches.
Now, PLEASE don't emulate what I did UNTIL you get the bore size accurately measured in your Bess. Some ran larger than that, but some ran MUCH SMALLER than .750 inch and especially ones like you have.
Le Loop is correct you DO NOT load the pan before the cartridge or separate powder/card/cushion wad/PRB. They did that in War because they had to and they accepted some horrible accidents by loading the pan first. That is something we don't need to be "authentic" about.
I prefer leather flint wraps around my flints, but one thing I learned in reenacting was each musket may prefer one thickness of lead and one length of flint to spark consistently and the best. So in my unit's muskets, I wound up trying different length flints with different thicknesses of leather. Some folks use lead wraps and a few had good luck with them in their Besses, however I never did and most Besses I worked on for our guys like leather flint wraps. It didn't matter if the Bess was made in Italy or Japan.
Finally, the Bess has a HEAVY standard Military Trigger Pull that is difficult to shoot for the best accuracy. On most Besses, I advise you find a qualified person to do a trigger job on it for the best accuracy.
Gus
If I was actually being attacked in such a manner, I might consider priming the pan first. 
