looking for advice on cleaning old equipment

Hello Classicquers, I have some vintage DEC equipment (terminals and small systems) that I need to clean up. I'm looking for advice on how to clean the plastic bits. Specifically, I want to know if anyone has a good solution to preserve labels that are attached to such plastic bits while they're being cleaned, especially labels that can't be removed (e.g., paper labels). In the past I've cut out pieces of Saran wrap just large enough to cover the label and then covered that with painter's masking tape.? Unfortunately it wasn't perfect and some water/soap did get under the tape and reached the label (this is especially problematic if the plastic surface has some texture). I'm hoping for something like a wax or some other kind of material that is easily removed with heat but at room temperature is impervious to water and soap. Does anyone have any ideas, good or otherwise? Thanks! --Bjoren Davis