Any ideas as to the removal of stains on enamel?

[Warpy]

5. It's probably discoloration from grease aerosols

so my best advice to preserve the finish completely is to wait until summer, spray it down with household ammonia and tie it up in a black trash bag in full sun until late afternoon. At that point, you should be able to wipe it right off as heat + ammonia + grease produce the saponification reaction, meaning the hard grease turns to soft soap. It will likely not smell very nice the first time you turn it on as all the stuff you couldn't reach inside the vent cooks off, so plug it in outside the first time.

Any abrasive cleaner, even toothpaste, will remove the surface shine of the enamel over time, causing the grease deposits to occur more quickly. About the only suggestion I've read here that can be tried now is the Magic Eraser. Oven cleaner might work, but again, it has to be heated in order for the saponification to occur and uses more dangerous lye in place of ammonia.