I am kinda late to this thread.
Based off of my 22" WSM, start with a full fire ring of charcoal, don't worry about wasting charcoal you can kill the fire when you are finished and reuse it next time.
I use a foiled water pan, dry, no heat sink.
Light 15 -20 briquettes or if you want high heat faster light more (I use plain ol' Kingsford blue lit in a chimney) poured across the top of the coal bed.
Add wood chunks on top of the lit coals, quickly assemble the WSM and put the meat in immediately.
Start with all vents fully open.
As temperature approaches 20 degrees less than desired temperature close one intake completely.
If temperature stalls open the vent 50% and fine tune accordingly.
If temperature is still rising close second intake completely when temperature is 10 degrees under desired temperature.
If temperature stalls open the vent 50% and fine tune accordingly.
If temperature is still rising close last vent 50-70%.
Depending on how the WSM is responding fine tune accordingly.
You should be able to easily achieve 300+.
When finished cooking close all vents 100%, fire should die.
Give the fire plenty of time to go completely cold before opening the lid because if it is not out it will restart.
Save the left over charcoal and use it for the next cook.
FWIW my WSM is only one week old, I have cooked two chickens and one brisket, I have had no problems controlling the temperature 325 for the chickens and 240 for the brisket.
Measured on the grate with a Maverick thermometer.