I apologize if this has already been summarized somewhere but I'm using an app on my iPod to look at the boards and I can't figure out how to conduct a search.
I usually fill mine up and then close all the vents when the smoke is done.
Save what's left for the next smoke.
Congrats on the 18.5.
I have one and love it..
Just started an all nite smoke for the first time a few minutes ago.
Like the others said. I fill it and I don't have to worry about reloading if I didn't put enough. I noticed tough that when I close all vents and let the WSM cool down, I get rust like residues on the side and lid . Removing CAREFULLY the water pan before closing all vents seems to take care of the problem.