My vet prescribed a human acne cream with benzoyl peroxide for our Bunnelina's feline acne, but it was too strong and irritating. After she recovered from that, I was able to scrub off a lot of the black, waxy "acne" material with an old, soft toothbrush and mild soap. After I did this a few times, she improved a lot and eventually it went away without medication.
(We hoped that her pristine chin would help her get a date for the prom, but alas.)
It's so important to keep cats' food bowls immaculate. I've always used glass, and as soon as I see a film developing from the kibble, I clean them. Grease will cause acne whether you use plastic or glass.