Pillow ticking is popular, because it's a nice tight weave to keep the feathers from sticking through on pillows.
The size is somewhat limited as most PT is .018. You can find some other sizes by measuring a bunch of different material.
I always cut my patches at the muzzle and use Mink Oil for lube.
Sabot....I see a bottle of T7 next to your patches. Is that what you're using? It's hard on patches. I use nothing but real BP with a PRB.