I'm not an expert at all about beardies, but I'd think that you would be best to leave him alone to brumate and bathe him when he awakens. I very well could be wrong, but I figured some input is better than none.
Yeah I wouldn't introduce something new like that during brumation. Baths aren't necessary but are nice if they get stinky. You can offer water by just dripping some on her nose using a plastic syringe or dropper so she can lick it up.