I love giving massages. I have found the feet to be highly sensitive since it is the end-point to all nerves in your body.
That being said too, as a man who loves to give service attention, women should treat their feet like they ask the "men" who request certain favors.
If one desires that kind of attention, bringing a bowl of water, two towels and some soap can be a signal to their partner to please take care of me.
But remember no two people are the same, orgasms for one may lead to a "ticklish" good time for another, but hey .... if one is into power play .... well #snicker, it is a fun way to cause "sensation" without pain but still conform to the traditional tropish view of SM....