1 cup of paint [Crazy colour of your choice]
2 tbsp powdered tile grout [Not Sanded]
Any excess paint needs to be discarded as it doesn't keep well, keep this in mind and adjust
recipe to suit to avoid waste.
haven't tried this but apparently the way to keep the blackboard looking 'as new' is to soak a cloth in coke and clean it with that?
Just a thought...
as well as a wall or reconditioning an already existing chalkboard how about considering painting the side of jars in the pantry to use as labels or containers in your sewing area?