Back on topic of dunk sparing the grain bag, I have done it, and it works well.
Recently I have been practicing a pour over sparge withe the grain bag hanging over the kettle, perhaps not quite as efficient, but much easier...I like easy btw.
The added benefit of the pour over sparge is that you simply sparge to your pre boil volume. Basically I just eyeball the main mash strike water volume, them fine tune with the pour over sparge to hit PB volume. No calculators, no measuring just RDWHAHB and all is good.
Typical sparge is about a gallon on a 1/4 keg, 8 gallon batch.