I use denat alcohol for degreasing tires and wheels prior to glueing. Sounds like the soap and water was ok on 3 of your 4 wheels, but for some reason the one you're having probs with, it didn't work as well.

Anything that will let you suspend the tire/wheel and allows free rotation can be used as a balancer - look at an airplane prop balancer in somebody's catalog, you'll get the idea. Lots of things used to the balancing - lead tape is prob easiest.