If you're having trouble working up the nerve, you can ask your partner to paint your nails. Say that it would be romantic, to be all close and holding hands, that you'd like them to learn how to paint your nails. Chat while you're getting your nails painted, and perhaps offer to paint their toenails. Nobody would see under shoes! It'd be fun; it kinda tickles!
That might break the ice a little. Then again, it might fall flat if they get shy or spooked.
