One good thing about saving washed prints, then toning all of them together later is that your exposure to selenium vapors is reduced.
No one mentioned that here, so maybe it's not a big deal, but my initiation to selenium toning included that advice (by Fred Picker). Be sure to ventilate well when you do this, and, as others have said, soak thoroughly. I usually put all of the prints into a deep tray to soak in clean water before setting up to tone and rewash.