I put on sunglasses then put the Schuberth's sliding shade down HALFway and look under it. The shade acts like a visor. Tape probalby works better.
BTW blue painter's tape is removable for only a week or two. For permanent, 3M makes high quality light-blocking tapes used in photography, graphic design, lithography, industrial applications, etc. Ask someone works in a sign or graphics shop to snag you a foot or two. Aluminum tape used to seal HVAC ductwork is a favorite of photographers for homemade gobos and snoots (shields to modify the field of illumination and control spillover from a strobe). Black gaffer's tape works too; be forewarned, though--if you need to move or remove either or those, you'll be buying a new visor.