I agree with Sure Shot, regular old FFg or FFFg made into smaller pieces should be more than adequate as FFFFg for priming - at least most of the time.
I am getting started in making my my own BP, don't have all the pieces yet; but I have been haunting the pyrotechnic forums since those guys make and burn BP by the pound.
The only hiccough I can think of - presence of sulfur reduces the ignition temperature of the mix. So if you have a mix of say 20% charcoal with 80% nitrate - no sulfur - it sill likely burn fine in say an inline rifle using a 209 primer, but the lack of sulfur might make it hard to light in the priming pan.
IIRC sulfur free BP lights around 440C, BP with maybe 8ish or so % sulfur lights around 300C.
The way around that it is to take some of the FFg in the can you got, make it into smaller pieces and see if you are getting hot enough sparks to light it in your pan with your flint. Which is exactly what sure shot already did.
FWIW I might be off base here. All my experience so far is with BP subs and primer ignitions. I did used to have a cap lock muzzle loader, but I used subs only in it and sent it down the road.
From reading about it sulfur makes the smoke nice and white(r) rolling out the muzzle, and lowers the ignition temp.