Actually I would just look for a thicer patching material, just make suer it is 100% cotton.... Pillow ticking is cheap and comes in a couple of thicknesses. Just pic up a yard of it at the local fabric shop and take it home and wash it before using it. That usually puffs it up a few thousands.
I would advise against using 2 patches as there is the possibility the outer one might separater from the inner one and remain in the barrel. If smoldering things might get a bit more exciting than you want when you pour the next charge in it. If it were me I would use one patch with pillow ticking lubed with crisco and see what happened, then decide what you want to do. How think you can go is going to be limited a bit by what size round ball you are using and the bore diameter to a degree.
It really depends on what you are expecting out of the rifle. If your plans are to enter target matches with stiff competition like at Friendship, then replace the barrel. If you are looking for a squirrel rifle with open sites well then you might be just fine with what you have even if it occassionally tears a patch since most of your shots are gonna be under 50 yards. Same goes for deer as lot of white tail have been taken with rusted shot out 30/30 winchesters over the years.
Get your powder, caps (or priming powder in the case of a flintlock), some balls, your patching material, crisco and your patch knive with short starter and range rod and head on out to make some smoke. If a cap lock pop a couple of caps, charget the rifle, a good rule of thumb is use the same number of grains of powder as the caliber so in this case 36 grains of 3F. I suggest cutting strips of patching material, grease it, set it over the muzzle, short start the ball flush with the muzzle with the sprue up then cut the patch, run the ball down the bore about 4 inches with the short starter, then the rest of the way down the bore tight on the charge. Cap or prime the rifle and fire at will. Try and do this over an area that it will be easy to find the patches and look for them after each shot.
Good luck and let me know how things turn out..
DonT