Handshake Door Handle
I don't know if we'll ever be able to go back to shaking hands again, but just in case, I think it's best to keep practicing so I don't forget how. Oh hey, a Handshake Door Handle! Built-in practice on a firm grip and warm grasp every time I open the closet. Or the pantry. Ooh, or the bathroom door. Having to shake a hand after each pee and poo might also encourage me to wash my hands.
The only thing missing from this handshake trainer is the eyes you must also look into during the shake to maintain proper form. But that's an easy solution. Just get a set of googlies along with the Handshake Door Handle, and stick them on the door a few feet above it.