I have a USB scope. It's ok but nothing real fancy.
A jewelers loop or something would work better IMO.
When they are small, its not just how much you can magnify but its also what kind of shape the molt is in.
Try to get to it as soon as it happens, before it dries out. Pin it open and take a look. When its dry, put it in a little humidity box then pin it open.
If they ball up their molt forget about it and wait for the next one :p