It depends on your fridge, I suppose. :-) I think the poster meant "desiccant".I don't know what a "descant" is in this context (unless I have to find a contratenor and put him in the fridge, but it seems impractical ).
I wasn't aware that there was any special risk of fogging with a polyester base. Is it just an issue of light piping? I've used a small amount of 35mm on polyester bases, never treated it specially, and don't remember seeing any problems, but maybe I was just lucky.