You might want to buy some after market nipples and get caps to match them. The cap fit is important. The other idea is to use wads. These are manufactured and lubed. You can also make your own. I've done both but making your own doesn't save that much money so now I just buy wads. So you put in the powder charge, say 18-20 grains fffg and then a lubed wad and then the ball. No need to use Crisco or something else over the ball. There cannot be any air space between powder and ball so exert enough pressure (within reason) on the loading lever until you hear a slight crunch of the ball over the powder, or simply snug if you use a wad. The closer the ball is to the front end of the chamber, the more accurate the load is- generally speaking. Very often a larger powder charge is more accurate, that is, some folks use only 10 grains and put cream of wheat or some filler on top to take up space but in my experience a larger charge 18 gr plus- is more accurate.
A lot of chain fires start on the first load of the day. We talked about this a few years ago. If the nipples are oiled after cleaning, the caps might slide off from recoil. At the start of a shooting session, fire a cap on each nipple to burn up any oil and then load.