They are worth every penny. It's for removing dirt and grime not rust. Rust needs to be removed with evapo-rust remover. To polish items you need a buffer or tumbler. If your plastic post have any grime or wax left on them your doing something wrong. You need to use a degreaser or some homemade formula to help. Water alone does not work well. I'm not aware of anything even close to an UC besides hand brushing. Who wants to hand brush nasty parts? I like the Harbor freight one for small jobs (water heats fast) and the big 3gal one for large items like wire harnesses.