Hi Bernice: What I use is a paste of vinegar and cream of tartar (the dry stuff). Make a paste and put it on the gunk. Let it sit for about 15 or 20 seconds and then scrape off with a plastic putty knife or one of those plastic scrubbies. You may have to do it a couple of times if the gunk is thick, but usually not. There is no smell and it is environmentally safe. Good luck.
I remove and soak in hot water, then use soft scrub and a scrubby.
Bar keepers friend
I soak them in hot water and Dawn dishwashing liquid that I get at the dollar store (a little goes a long way) and then I wipe them down with paper towels and rinse. The Dawn really cuts the grease.