Besides pans, et al. You might want to consider a large plastic (trash) bag. Spray down with some oven cleaner or some Dawn Power Dissolver which is what I use all the time for a pre soak (no water, spray only) for cleaning grates. Spary with the oven cleaner or DPD, and shove in a bag - sit overnight. I usually only use DPD spray, let it sit for 30 - 60 min then soak. I you can't soak then just scrub away.
I use the laundry tub in the basement. The WSM grates fit fine, the Performer grates are a little too big, but I just spin them around to let the other half soak. I have my water heater on high (no little kids around) so I have very hot water for overnight soakings.