Agree that with a lot of colonies the Snellgrove board method would be very time consuming!
The Cloake board however is a very useful tool in queen rearing.... basically a framed queen excluder with one entrance door ( closeable) at the front, and a solid board that is slid over the queen excluder.
David Woodward in his book Queen Bee: Biology, Rearing an Breeding describes the Cloak boards use in understandable terminology.
Basically to split 2 full brood boxes and stimulate an emergency response for cell building with the cloak board slid in ( from the back) and closed, between 2 broods .. with queen in bottom box,and top front entrance opened to allow a top entrance ( bottom box and floor rotated 180 degrees... and then 24-36 hours later the Cloak board slider removed,the full length sine above the qe closed off with a strip ... which sets the colony up as a cell finisher, in supersedure response mode.
Easy Peasy!
Yeghes da