The ST's are sealed units, so brining isn't necessary for moisture, but if you like the flavor of the brine, go for it! Watch your internal temp, and I'd recommend some type of remote-read thermometer, so you're not opening the door to check temp. Opening the door causes huge moisture losses. Too high an internal temp will cause drying much more so than smoking without a brine.
I'd recommend something really mild like apple or alder, but whatever your tastebuds like will work too!
Let us know how things turn out. I also recommend a little notebook to keep track of your successes and failures. It'll help you develop a catalog of recipes you can keep going back to.
I believe in catch and release fishing. I don't want to EAT 'em all, I just want to GREET 'em all!