Well, most of this was said in the descriptive titles. Two hens setting at once. One I need to let rest, but I like her genetics. Anyone ever successfully switch eggs on a hen?

You will have no problem doing that at all, just don't overload the next hen with to many eggs though.What you might be better off doing is allow both hens to hatch there eggs ,then transfer the chicks allowing the hen that needs the rest to raise perhaps one chick giving yourself some options.

transfer, and it should be perfectly fine, just ensure you check later to see the hen has adopted them into the nest. (you may also want to mark them to know which ones were the other hens)

Transferring eggs should be fine. I do it frequently. Make sure you wash your hands first and try not to shake/jiggle them as you move them. Don't overload the foster hen with too many eggs however. Alternately, you can actually remove the other hens eggs and have her incubate just the foster eggs. Show budgie breeders will do this so as not to put too much strain on their birds, to maximise the likelihood of chicks from top pairings and/or where pairs are unreliable incubators/parents. If your hen (the one you like) has already produced 2 full rounds of chicks I wouldn't allow her to incubate and hatch any eggs herself. It puts too much strain on a bird. I rest my budgies for 6 months minimum after 2 clutches.

How has all that gone for you?