Scudrunners

I might suspect that polarization might
be another way to do this, as well.

Put static-cling stickies polarized vertically
on the window, and make the student wear
wraparound sunglasses that are polarized
horizontally.

He can see inside the cockpit just fine, but
the windows would appear black.

I would apply for a patent for this, but
I'm sure someone else has already
thought of it!

What I found was the most important part of doing all my instrument training using two stage amber was when I finally started flying in cloud it seemed normal.

As far as wearing a hood goes I never used one and refused to wear one for my instrument check rides.

That's fine on the island but here on the prairies you can freeze you ears off if you don't wear a hood. Winter's coming and those Cessna heaters are crap.  :(