To answer your question, try .010", .012", and .015" thick patches in that .36 caliber gun. Like with any new gun, you cannot depend on what the factory says the caliber is. You have to measure the lands and grooves with a caliper. Normally, you will load a cast round ball that is .010" smaller in diameter than the land diameter( some shooters load a ball that is only .005" smaller, and some insist they get best accuracy using a land diameter ball). The groove diameter affects how thick your patching has to be, as the patch not only grabs the ball to impart the spin of the lands( rifling) but it also tries to fill the grooves to prevent gase from blowing by and cutting both the patching and the soft lead ball. Some of the patch thickness that is caught between the ball and the lands will push to the side to get into the grooves along with the cloth that is over the grooves to begin. Mostly, the cloth over the grooves is what will fill the grooves, and the lube on that part of the patch is what will lube the grooves to prevent fouling from caking in the grooves.
You want a well lubed patch to lube the lands when you load the PRB down the barrel, and to lube the grooves as the ball is fired out the barrel. If you want the grooves lubed well before the PRB is fired, Then use a separate cleaning patch to lube the barrel after the ball is seated on the powder, or OP wad.( The OP wad will seal the grooves for the patching, so that the patch needs only be concerned with lubing the grooves.)
