I almost never fire up my 22.5" Kettle or WSM without reaching for one of my two 15" carbon steel Paella pans. As accessories go, they're pretty inexpensive, about $22-25 on Amazon. I have one by Magefesa and one by Garcina. I also have two 13.25" round cooling racks by NordicWare, about $14 each on Amazon. The 18" paella pans will not fit on the 22.5" Kettle or WSM. The 15" dimension is the diameter of the pan. With the handles, it ads another 4 inches. With the 18" pan, the handles and another 5 inches, so you can't use the lid. Trust me, I tried.
I use these pans for drip pans, fry pans, baking pans, pizza pans, smoking pans, you name it. Heck, I've even made paella..........once. They keep the Kettle and WSM free of gunk, are easy to transport cold and hot meat and veggies to/from the Kettle or WSM, and are even easy to make resting a breeze. I've used them not only in the Kettle and WSM, but on the stove top and in the oven too. They are my go to pans for just about everything.
For care, I wash, dry immediately, spray with any oil, wipe the oil around the pan, and stick it in the cabinet. Spraying the pan and cooling rack with oil before use makes cleanup a breeze.
My wife got tired of all our roasters and kitchenware getting discolored by the smoker and Kettle. The paella pans solved all that.
I still do on occasion use 9x13 aluminum roasting pans, but usually only for beans and mac n cheese. I have a turkey roaster that gets used too on occasion for large batches of vegetables. For the most part though, its the paella pans that are the workhorses around here. When you consider the costs of all the different pans you can use, having one that can do it all is a money saver.
Here are a few pics.
What they look like when new:
What mine look like now: