The few people I've seen skin birds, as well as myself, use small surgical scalpels.
As far as preserving the skins while you're at camp, I honestly believe you won't be able to keep them from drying out. I know skins have been kept in freezers for years, but they were encased in a block of ice. I'm thinking, and do not take this as a "yes it will work", that a bucket of water would work for a few days, but I don't know if the skins would spoil or not.
There are no ducks in the desert!