TTD has confessed, in another thread, that his ticklish spots include:
Tops, soles, arches, heels, sides, toes YIKES especially the area under the toes and the balls of the feet!
So you don't have to be creative. Just be extreme. Make sure that he is tied down securely, ankles immobilized and tie back his toes. Then experiment with half a dozen different implements on the spots he has mentioned, and be persistent. Start with one hour, and see how he's doing. 😀
Have a great Valentine's Day, both of you.