So, I resorted to bribes. For each foot, a piece of carrot. Eventually, we got to a piece of carrot after all 4 feet.
Spring forward several months after not riding him. There I am, picking his feet just like always and he refuses to give me the third foot. I just look at him as if to say, "really?". So I start brushing and let him think about it. Went back the offending foot, and he gave it like a charm. And he got his treat after the 4th. Guess he remembered. LOL
Still miss that stubborn old coot!