My .36 is a T/C Seneca and I shoot 25 to 30 grains of Pyrodex P behind the patched roundball. When my gun was new it shot and loaded best with .010 lubed patches. Broke the ramrod trying to load the recommended .015 patch. Now that there's some miles on it, the .015 patch goes down easier. If a friend hadn't encouraged me to try the .010 patch starting out, I probably would've gotten frustrated and given up on the gun. I've had best luck with patches pre-lubed with Wonder lube or Bore Butter.
If I stick with Pyrodex P and the relatively light load listed above, it will shoot accurately all afternoon without cleaning. Shooting offhand at 50 yds, the gun just chews the center out of the target...and keeps doing it until I get bored! Loads as light as 15 grains worked reasonably well, but accuracy seemed best around 30 grains. The 40 & 50 grain loads in the T/C manual just fouled the barrel, made loading tougher and accuracy worse.
Even though this load is light, it's almost too powerful for squirrels. My favorite for squirrel is a T/C System 1 with .32 cal barrel loaded with 10 Gr. Pyrodex P. Out to 50 Yds. performance is about the same as a .22 long rifle. In your gun, 20 to 25 Grains of Pyro-P would be plenty. You'll use so little of it, a pound will last a long time.
Pyrodex RS and Select, being slower burning, would probably foul more than Pyrodex P; not recommended.
Take good care of that baby. Not everyone is lucky enough to own one.
Bob