Try goo gone. They have it at home depot. It seems to work wonders on everything else
My water bowl is covered in foil. I never use water in it anymore, and I tend to not clean it...ever.
A buddy's isn't even foiled, it's just well seasoned with yummy smelling burnt grease.
I think as long as you use your smoker regularly, it's not a big deal. If you don't use it for a while and it gets funky, run it hot to burn out the funk without any food before the next use.