I'd suggest cleaning it really good with a solvent, then dry patch it until patches are clean. Then make sure you put anti-freeze grease on your powder drum screw threads. Make sure you keep any oil out of the powder drum area or it'll get all plugged up once the BP hits it. Then use a good lube on your bore and let it sit overnight. Finally, next day, go outside and prime your pan and fire it without a charge. Should have smoke come out the end. Once you're sure it'll work, keep shooting as it will take a while to break it in. I'd probably get ffffg priming powder by Goex or one of the regular bp's and use ffg of the same brand for your charge.
I typically also disassemble the lock, remove the barrel from the stock and oil up the trigger mechanism internally and the barrel channel to avoid water getting in and rusting things. I also check for burrs on the contact bar where the trigger pushes up on the lock. if it's choppy or gouged, it'll make for a tough trigger pull. I put a light coat of 3-in-1 oil all along the outside of the barrel, on the hammer and sights and you'd want to avoid it on the frizzen/pan area.
