I like the term "knack"--- I've always called it having "the gift"...it involves the traits on the list such as empathy and finesse, common sense, using elements from the life story, humor, flexibility etc but also a few I have noticed that are not on the Knack list such as being creative, (maybe that is what you call flexibility), and also being happy. Happy (optimistic) optimistic people seem to be very effective at what they do. Essential to all of this is being intuitive and sensitive, so that the caregiver can pick up cues and be able to meet the needs of the client. The person must be skilled in reading non verbal cues and in feeling what people need. If someone has this knack, she almost always knows what to do.
We always use "the knack" in our work setting because we are with the client at home. The caregiver has to care for the client and keep her safe and well cared for without any help from outside resources, such as a staff of other caregivers.
One example is the bathing. Most clients don't like to have showers. It requires every knack in the world. One especially talented caregiver with knack sets the client's hair in pin curls ( a lost art!!!) after the shower. That gets the client in the shower.