A couple of questions.
How often should you sharpen the flint? And what process is best?
What type of flints do you prefer and when do you change them?
Is there anything that I should be doing to the frizzen?
And how often would you replace it?
The rifle came with an agate. You do not sharpen them although I have always been tempted to hit them with a diamond wheel and see if I can get a few more shots off it. When the agate wears out, you go to Thomas Fuller Black English Flints. You will know when they need to be knapped when they stop sparking.
The best way to knapp is set the hammer on half c0ck. Then with a striker set at the edge of the flint chip the edge off and sharpen it. A very small flake will come off. Sometimes you don't even see it. But touch the edge and you will feel it. If it just will not sharpen, flip it over in the jaws and try that. Or change it out. I average around 30-40 sparks per flint.
The frizzen will soften with use, but your talking thousands of shots. You can harden the frizzen with kasonite and a torch, but I have never done it. I've shot my Trade Rifle for many years and the frizzen is still fine. You will tell when the frizzen is going back because the flints will start cutting deep into it. As long as it sparks.. keep shooting.
My .54 trade rifle likes 90 grains of 2f black powder and a .530 patched ball.