Disclaimer: I'm not an expert on this subject.

Absolutely I think you should use a dry chemical extinguisher on a person. I've seen it done and the person suffered no ill effects.

It was a training class for military personnel who were being posted to a remote location. A senior NCO who obviously hadn't paid attention to the firefighters' verbal instructions walked straight up to a metal bucket filled with water and burning gasoline, pointed the extinguisher straight down, and let it go full force. In other words, he did everything we had just been carefully told NOT to do. The burning gasoline splashed all over his legs and feet, setting his trousers and boots on fire; he sprayed himself with the extinguisher before he could suffer any serious injury.

The one you shouldn't use on a person is the CO2 fire extinguisher; because of the extreme cold it generates, you can cause severe frostbite (or so I was told).

ABC means just that - it can be used on any type A, type B, or type C fire.