I always let the WSM run empty a while after lighting & before adding meat(30-45 minutes), get the temps settled, and then go.
I use the KISS method(similar to the minion method, and close the bottom vents down at different times depending on what I am smoking). I really dont have an ssue with the door leaking, and during the really cold days I was smoking (below zero), I had the door on upside down to keep the temps up.
Havent tried sand, and doubt I will,
The large water pan is a big improvment over the older models, and typically not an issue , something always needs to be flipped, moved, added or pulled off, so I add water then, no real issue with temp spikes from an emptying water pan for me.