Painting porcelain-on-steel chalkboards

We just bought new chalkboards with surfaces made of porcelain on steel. Unfortunately, since our school is art-based, our teachers make daily artwork on their boards. The chalk does not adhere that well, or blend itself as evenly on the porcelain surfaces as it did on the old fashioned ones. We are planning on painting them over with special chalkboard paint but wonder what kind of prep work will be needed to make the paint adhere to the porcelain?

I was told once that as a general rule of coating "you can can not plate superior plating on the un-prepared surface, but you can plate poor plating on a well-prepared surface".
Basically, the same concept applies here, and I doubt that you guys have the time or money to waste. Of course try this on a small portion of the board first and see how it works.
Clean the chalk board with most anything (soap and water).
Maybe clean it with acetone ⇦ on eBay or Amazon [affil link] Flammable! afterwards.
Make sure it is dry but do not wait until dust and things adhere to the board again.
I do not know much about porcelain, but sanding the surface is common before painting. Clean after sanding again.
I would suggest a primer coating (spray paint,etc), because most primers are made for good adhesion.
Let it fully dry, and very lightly sand the primer. Clean again and let it dry.
Apply the chalk finish in probably 2 coatings.
This is just basic practice for many coatings. I hope this helps.