I used an aluminum hot water heater drip tray for my 22" and I had to get the tin snips out and cut notches in the pan edges for the legs. Even though the legs stick out past the pan the vents on the WSM are still protected by the pan.
For lighting my chimney I used to rest it on my my gasser grill but I was afraid of the lump falling out and going through the bottom of my gasser so now I use an old baking pan and put it on top of WSM charcoal ring.