I happened to see a spray can of oven on the kitchen counter today as I wal ked past on my way to the rec room where our fireplace is located. Instead of the stuff I usually use to clean the glass fireplace doors, I thought t hat if it cleaned dirty ovens, it might work on the fireplace doors.
I tried it on room temperature doors, the crud on the glass and metal door frames just ran off into the workshop sink where it easily washed down the drain. A light once-over with a coarse sponge and the doors look like new. Wish I had known about this years ago.