Looks like I'm your answer man for the moment, Al.
You can split the chickens, beer cans inserted, between the top and bottom grates if you like but I've actually cooked as many as 8 beer can chickens at a time in a single 18" WSM. You shouldn't have any trouble making them fit on one grate if you choose to go that route. If you do, I would position them so that their backs are all toward the center and the drums splayed toward the outside. This will give you better results on your skin as well as the meat.
I like to cook beer can chickens hot, somewhere in the 350°F range but that's just me. I think chicken can get kind of rubbery if cooked at low temps for a long time but, again, that's just me.
I would not wash the brine off the birds before seasoning them. Instead, just dry them thoroughly with paper towels and then apply your rub.
As for smoke wood, I would recommend using a fruit wood like apple or cherry as they impart a nice smoke flavor without overpowering the more delicate poultry.
Remember to rest the birds under a foil tent when they're done!