I've seen the question posted a few times recently, so thought I would share how to get to 350 degrees on your 22" kettle consistently. There's a ton of ways to skin a cat - this is just how I do it.
Overload one charcoal basket, vents wide open and you're pretty much done. I place the basket on one side of the kettle for a two zone fire. Initially, your grate thermometer will probably read about 375, but will drop once you get some food on the grill and it settles in. Dome thermometer will read around 400 throughout the cook or at least mine does. This is good for a little over an hour.
I've never tried making manicotti before so thought I would give it a stab. Pretty good.
Don't be jealous of this clean grate.