I have a lang 48 not the 84 so your fire management should be similar just bigger.
I split this size chunk in 2 pieces
when the fire looks about like this, lay the chunk on the grate and then push it back with a poker as far as I can. If I want it to run hotter put the piece in sooner, cooler wait a little longer. 250-300 is my normal range using hickory or pecan vents and damper wide open on the factory lang grate. Haven't tried any charcoal yet. Once again I only have the 48 but when I bought it Ben Lang told me to run it wide open and so far so good.