If you graft cover them with a damp paper towel as soon as you finish each graft. Make your cell starter population really dense, and give it a nice pollen frame right next to the cells and a honey frame on the other side, and start feeding as soon as you set it up. Make the starter hopelessly queenless (not
only queenless, but lacking
any larva that they can start on their own) long enough in advance that they are raring to go when you give them the grafts - 24 hrs or so. Feed until the cells are capped. Check for wild cells 2 or three days after you make them queenless just to make sure.
I've only been messing with queen raising this season, and I'm basically tipping you to not make the mistakes that I've already made this year. Made 16 nice cells out of 30 grafts on my last try though. I finally got a bit of success using a nuc with nothing but a bunch of nurse bees shook in with only a frame of pollen, and a frame of nectar and empty frames to fill it.
2 day old cells.