I've got a .54 cal Lyman Deerslayer that was fired little & insufficiently cleaned before passing on thru hands of subsequent owners. Despite a couple of pits near the muzzle, the bore looks clean.
For now, I use Pyrodex RS exclusively - Pyrodex P may be more appropriate for your .50 cal if you can't access real 3F BP.
One often overlooked section of the ignition system is that nasty little channel that makes a righthand turn for the cap fire to negotiate.
It's a good idea to remove the cleanout screw and the nipple every time you clean. scrub thru the nipple hole with a .22 bore brush, and use pipe cleaner material (in the 21st century, younger shooters may recognise it as "AR-15 gas tube cleaners"). You may think you're pretty good with Q-Tips - if so, go for it, but keep in mind that you need to guarantee you're not leaving any Q-Tip fibers behind in the flash channel.
With my rifle, it was necessary to not only clean out accumulated crud, after removing the cleanout screw, but I also had to scrape out rust & junk with a wire twist drill bit. You don't want to necessarily bore it out, just scrape it by hand down to clean metal. If you have an older caplock rifle that hasn't had the flash channel cleaned out after EVERY use throughout the years, you will find that a lot of stuff will scrape out & your ignition will magically improve.
Oil it up for storage & put a dab of grease or anti-seize on the cleanut screw.
Now, prior to loading & firing, be sure to cleanout the drum or snail to ensure there's NO residual oil left. For some rifles, folks are able to just pop a couple of caps to clear out residual oil, but in a more sensitive set up such as yours & mine, you end up with more evenly distributed oil along the channel - now also having a fine layer of primer soot stuck to it.
Use whatever patch lube you like - yours will be better than everyone else's - but only because it's yours. Talk to 100 shooters & you'll get 100 lube recipes - every one is better than all the rest ...
In general, it's advantageous to saturate ball patches with a melted lube that soaks into patch fibers then solidifies. If you can pour out a lube onto a patch it's too thin, unless you take the time to work it completely into the patch material - proponents of spit, Moose Milk & olive oil concoctions will disagree, but remember THEIR stuff is all better than everyone elses' too.
And, since someone will ask: I use a blend of tallow & beeswax, and it does have just a little olive oil in it, too :wink: