I also do herms and fly sparge, I just disconnect the pump inlet from the drain on the MLT and connect that to the HLT after my mash. I open the valves and spray the sparge water into the MLT via a sparge / spray bar until I get a nice layer of water over the grain. I then drain into the BK and close the valves until its almost a drip both into the MLT and out of the MLT. I do 20 gallons so it takes at least an hour if I'm rushing, but I try to take 1.5-2 hours. I find other things to do, like clean kegs, during this time as it is completely hands off. I push the sparge water through my IC that I use as my herms hex, cleans it up nicely.