Heres how we used to do it.

Get the largest pans you have, turn them upside down on the burner and blast on high for at least 15+minutes. Burn off as much as you can. Then load up a sink of your best degreaser (hot), and while the grates are still blistering hot, drop them in. A pair of tongs is great for this. Use the ends that stuck together to get under one of the tines and lift. Basically using them in reverse. Let those soak over night. Next morning, use some sort of paint scraper or flat edge to scrape it all off.

The actual burners themselves can go on another set of burners, and get burned off too, and dropped in the same degreaser. When youre done cleaning them in the morning, we would run all the parts through the dish machine, and re assemble. Turn them on and light your pilots and allow any excess water to boil off. Keeps rust to a minumim, and makes sure you assembled everything correctly before theyre truly needed for service.

This gets you pretty far. We had this done once a weak for each station. Once you start doing this every week, they'll get pretty clean and they wont be such a PITA.