As we move into the testing of Product B in preparation for a later release, I’m buoyed up by this article on using paper to prototype user interfaces.
To be honest I already do this, using drawing skills gained by disembowelling and drawing the corpses of small animals and plants during my Genetics degree at Queens.
Then I move it to something like OmniGraffle or Interface Builder (and more recently DashCode) before giving it to a UI and Icon designer for review.
It’s not quite tactile but until multi-touch interfaces become ubiquitous, it pays to interact with your paper interface using just a single finger and, to be honest, attempt to keep your arm straight. At this point you’re making a desperate attempt to emulate a mousing interface. It’s clunky but it works.