Do It And How

TIPS: read all before starting!
You don’t need very much ammonia. 1/2 cup is sufficient. More than that and you’re gonna be able to smell it, even with the oven door closed.
Hold your breath, plug your nose, do whatever you need to do to not inhale it. It is powerful stuff.
Before opening the oven door in the morning, open windows. Air flow is good.
When you do open the oven door in the morning, do so (with your nose plugged) and head out of the room for a few minutes.
After a few minutes you should be okay to wipe away the burnt on food without irritating your nose or throat. It should wipe up fairly easy. I had a couple of spots about an inch big that didn’t just wipe up that I had to scrape with my fingernail.
Never mix ammonia with bleach or any household cleaning products that may contain bleach! It will create a deadly gas.