Dave - od jeans are just great for patches- note that jeans come in many different thicknesses - from 6 ounce at about .008" to 12 ounce which is from .025" to .035" ( BOTH COMPRESSED measurements) depending on the tool used to measure it - ie: different calipers or mic's.
We mostly use store-bought denim in the 10 ounce range, which usually runs between .021" to .023" depending on the tool used for measuring. I use my mid calipers as being 'true' - actually an average, noting it here as either .022" or .0225".
With that patch, we use balls that are only .005" SMALLER than the bore size. In my .69 with it's .012" rifling depth, I use a .684" ball and the 12 ounce denim. In the case of my .32, I use a .320" ball in it's .320" bore, 10 ounce denim patch and it has ONLY .008" rifling - very narrow grooves and VERY wide lands- exactly the opposite scenario one might hope to expect. It shoots well with that combination - couldn't do any differently - it's almost a bench-rest or chunk-gun loading scenario. The .69 is also exceptionally accurate as well, as one might expect from the very tight fit of patch and ball.
So ----jeans?? My suggestion is to use only the lower frontal leg area and back of the leg above the knee, to avoid area of worn genes. The front of the thighs and calf areas are usually worn and will vary in thickness as well as in strength.
I've been using denim (I buy it by the meter or yard) since 1972 = 42 years - works for me and the rest of us, Taylor & LB, too.
Beware - "relaxed" and/or "senior's fit" genes are usually stretchy material that is NOT cotton. Use only 100% cotton. the burn test (of a few fibres) is the best way of testing.(outside the store) I have them snip off a small piece, take it outside and light it. If there is no oily smoke, nor stink of plastic and only dust left of the burnt cloth, it's cotton. If the residue it balled up material it has synthetic fibers and is generally not useable.