My Sahara is an terrible biter! One minute she's so sweet and in my lap purring, and the next minute she's chomping down hard on my hands or arms. When I pull my hands away and say, NO, very firmly to her, her ears lay back and she goes for my face. I tried putting her right down on the floor and ignoring her, and taking her to the bedroom for time out, getting her attention with a toy, everything would make her even more aggressive. Then just as quick as it starts, she turns back into my sweet little kitten again. I havent figured out what the cause is for this sudden change in behavior, and by the time I do figure it out, it will be too late or very hard to correct it.
This happened by chance or accident, which ever you want to call it....but the other day she started this attack on me again and I just happened to be eating peanut butter and had some on my hand. She chomped down on it and immediately stopped, backed away, and was shaking her head. It was a surprize and probably a shock, as she was expecting flesh instead of peanut butter. Since then when she starts up again, I grab the PB jar take a little on my finger and let her bite. She instantly stops and just walks away, and this has cut down on her attacks by a least 80% so far.
As for your feet, you could apply something like hot sause, solid deodorant, lotion, or something very sweet like honey, cats hate sweets!
I'm curing the devil herself with this method, it might help with your cats also.