Before I built my own flintlock my first one was a Lyman Great Plains in .54 cal. One of the first things that I did was order some extra flash hole inserts, I then opened them up slightly for better & quicker ignition. I will tell you that if you turned around and the rifle was fired you could not tell if it was a flintlock or percussion. I was kidded by the members of the club I was in, they said that now I would always be getting first place as I was the only one shooting in flintlock class. Well I told them that I would still shoot against them with their "Modern" rifles. I did and still took first most of the time. I have to say that the Lyman is one accurate rifle. I used washed Pillow ticking that miked out at .015 lubed with Wonder Lube/TC Bore Butter or the Remington version, they all smell like Ben Gay. I used .535 RBs and 70gr by volume of 3F (Target Shooting Only). The Priming charge was only enough to half fill the pan and I kept the chagre away from the flash hole so on ignition the flash would go directly into the flash hole. I used knapped flints (English) that I was able to obtain from Dixie at the time and from the Rondys I went to. One thing, your best accuracy will come after you have fired @ 50 - 100 shots thru the bore to season it and burnish it. DO NOT USE ANY PETROLEUM BASED PRODUCTS IN YOUR BORE IF YOU USE THE ABOVE LUBES, THEY WILL DESTROY THE SEASONING IN THE BORE.
Wonder Lube, 1000 Plus, TC Bore Butter are all natural products, when used they season the bore just like Grandma did with her cast iron cookware. These products will also provide excellent protection from corrosion. Clean with hot water with just a few drops of dish liquid in it. The water should be very hot, you can rinse the barrel with very hot (almost boiling) water. The hot water will raise the barrel temprature to where the excess water will evaprorate away, use the lube on the hot metal and let it cool. Wipe it down after its cool and apply another patch of lube in the bore. You can check it a bit down the raod and should not find any corrosion, if you do you didn't clean it completly.
I've done this for many years and have not had any problems.