I just use whatever I catch them eating as bait. Dry dog or cat food works just fine.
My spray-proof trap got me sprayed a little bit last week, so still be aware of that. You can wash off with dawn dish soap, baking soda, and hydrogen peroxide.
Had an old game dpt. trapper tell me the best way to kill them is a 22 or pellet gun lung shot. They're supposed to curl up and die slow and wont spray or release. My brain/spinal cord shots usually cause them to tense up and release.
As far as cats, I just leave them in the trap and turn the hose on em for a few minutes. Great aversion therapy, I've never seen the same cat twice.