My brewing buddy has made a move toward grain brewing with the purchase of a brewing pot equipped with a thermometer, false bottom, and screen in the false bottom with an attached valve. We can get to a mash temperature, add grain and hold temp with his burner unit if need be. Do we then drain the wort into a second vessel, batch sparge in the brew kettle, drain it off too and then clean the kettle out and add the liquid back in to boil? I'm just looking for the most efficient procedure here. Recommendations?
With one vessel and a grain bag, you're essentially doing the brew in a bag technique, popularized by our brewing friends from down under.
There are lots of you tube videos showing how to do this method, search for the term BIAB. You will probably need to upgrade the bag you use, however, as the normal grain bags given with steeping grains won't be strong enough to pull out the entire amount. (it's heavy with the water) Some use paint strainer bags found at home improvement stores, but those can be prone to ripping after a few uses.
All grain brewing is just soaking grains in hot water for a time, then either taking the water off the grain, or taking the grain out of the water. In single vessel brewing, you're taking the grains out of the water, then proceeding to boil.
You mentioned a thermometer, do be careful not to snag the bag on that. But with the false bottom, you should be able to heat your mash if it should fall too much after adding the grains.
If you have a boil pot and mash tun (two vessel system) you're limited to batch sparge. Use the boil kettle to heat the batch water, add to mash tun then lauter wort back to the boil kettle.
To fly sparge needs 3 vessels with the addition of a hot liquor tank.
If you only have the one vessel (mash tun) then you need to use a grain bag to remove the grain after the mash. Then the tun doubles as the boil kettle.
If your false bottom is a couple inches from the burner area you can apply heat during mash but it's really not recommended. Its difficult to get even heat through the mash even with stiring and often much of the enzymes denature near the burner. Best to insulate well and use a strike water calculator for temp and rely on insulation to hold it, unless you have a HERMS / RIS.