Teacher Tip-Use Spray Varnish

Take my advice and use a spray varnish if you are teaching a class. 
It must be oil-based.  You need to be certain of good ventilation; I generally spray the eggs out of doors, if it is not a humid day.  Spray the top half first, then rotate on a drying board, to spray the bottom half. 
You can see the set up below, as a student is checking to see if the eggs are dry...or need another coat of varnish.

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