With my Blichmann gear (15 and 20-gal kettles and false bottoms), it took me a good 6-8-10 batches (I'm a slow learner!) before I figgered out what others here recommend, i.e. use a constant and fairly healthy flow rate, and constant but very low heat. Blichmann button-louvered false bottoms seem to take a good bit of flow without getting stuck.
I was constantly messing with the pump flow, thinking slower was better, and actually created stuck sparges because (I theorize) if there is heat underneath the FB but little to no wort movement, that wort will boil, bubble up, let grain under the FB, and air/grain will get trapped in the pump. When you see the pump sputtering and seizing with trapped air and grain (as I have through numerous frustrating batches), it leads to a stressful afternoon debating whether you need to get all that mash out of there and start over...ugh.
Now, I mash in a little low, turn on the pump, stir thoroughly at the beginning while the mash temp is rising, and then leave it alone. Make sure there are a couple inches of wort above the grain bed during constant recirc. Very low flame on a Blichmann burner. My return is a silicone tube that rests just below the liquid surface with the help of a couple of floats (from the Blichmann Autosparge without the Auto
). When I make temp adjustments, I also tend to open the pump a scooch as well just to bump up the flow rate across the heat source. The hotter wort comes from underneath the false bottom and is deposited onto the top of the mash. It takes a little time to make its way through the bed, and then I back off the burner (or shut it off) when I'm actually a few degrees short of target...the heat at the top will make its way through the bed to even out. I would rather under-shoot and come up gradually. If it starts to drop a degree or two, turn the heat back on, but leave the pump run continuously.
A pair of Blichmann control modules on a Tower of Power is a couple of Christmases away, it seems. Until then, I think I've got my stuff dialed in fairly well.