I just resolved a bout of this... tried a few things, antibacterial wash and then hydrogen peroxide, but it wouldn't budge. I don't think it is clear weather it is oily food or bacteria, so you have to deal with both. I used only stainless steel, keeping kibble in freezer and only bringing out a bit at a time to room temperature. After not having success, I got a little bottle of a veterinary wash that contained chlorhexidine. I would microwave a small dish of water to warm it up, dip in a clean bit of cotton or microfibre cloth, put a drop of the wash and rub: side to side, up and down. Then I would wipe well with an unsoaped but wet part of the cloth.
I did this everytime after he ate; it cleared up very quickly and has not returned. I think perhaps rubbing alcohol is too harsh. You need to keep it clean, but not irritate it more.