... I plan on steaming the interior and exterior of the cook box and hit them as well as the Trim parts of the Lid with some HT flat Black rustoleum. ...
Am I misreading this, or do you want to
paint the inside of the cookbox? Brother, don't.
It's just raw aluminum in there, covered up in time by grease and gunk. High temp paint may stay on, but I'd imagine it'd stink for quite a while at there very least.
I forgot the picture. Here it is on one of mine, a DU code Silver C. I can't imagine Weber ever figured anyone would see it there, which is odd.