Fume boards are sold by many bee supply firms.  A fume board is a simple wooden frame the same size as a super, the same thickness as a super, and 2" to 4" high.  Tack a cloth tight across the frame.  Over that, tack a sheet metal cover.  This need not be a single piece, roofing tin works fine.  Fume boards work best when warm, so paint the top black.  To clear your supers:

• Attach the pump-spray cap and place your fume board in the sun, metal side up, to warm it.
• Smoke the hive entrance, and spray Bee-Quick onto the cloth of the fume board, using a zigzag pattern.
• Be sure to go to the edges of the cloth. Spray evenly over the entire surface of the cloth.  Don't spray too much.
• Remove outer and inner covers. Smoke bees on top bars. Place the fume board on the top super, avoiding large gaps.
• The super should be clear in from 3 to 5 minutes.  Repeat for each super, only spraying more Bee-Quick when you notice that the fumes have subsided. If many bees exit the hive, you have used far too much Bee-Quick. Remove the fume board more quickly .  Use less next time.
• If you want to harvest your honey on a very cloudy day, you may want to try a breeze board.