I am thinking about buying some used transformers because they're cheaper, but i'd like to know if there is a good way to wash/clean them? Since they're used.
I just use a water and disinfectant solution and some qutips. Don't put a lot of the solution on them and then dry them thoroughly. Another thing you can do is use a disinfectant spray but again don't drench them.
Be very careful with those, especially on plastics. They actually are very mildly abrasive, so you are not just cleaning a surface - you are actually sanding it. But don't just take my word for it - click.
If there's no electronics, then warm soapy water and gentle hands. I soak almost every used figure I buy for about 5 minutes, then lightly scrub them with a soft rag or sponge.