[ozo]

If the bore[smooth] is really dirty, and needs a brush,
that's what I use to get the funk.
Then a piece of cotton t-shirt on a string, solvent if needed.
Then the leather.

If you cut a round piece of leather [and try also with cloth]
and put a hole in the middle, run a boot lace thru the hole,
and tie it to a small bead...or button....anything that will
keep the boot string from pulling thru the leather.
But you get the picture....and there are other ways to fasten
it......just experiment.