Resolene can be applied with a brush, but using a cheap HF airbrush makes it so much easier to apply evenly. Resolene is more water resistant than Tan Kote, so if someone is sweating a lot I think Resolene will be more durable.
I normally use a liner on the inside of belts and I may or may not dye the inside liner - all depends on what look you want. If I am not going to dye the liner, I dye the belt first, then glue the liner on, trim the liner and then stitch it up, followed by final finish.
Gary