Question About Correct Electric Insulation Coating

Put your ceramic in a oven for a definite span of time. Heat oven and ceramic and release the moisture to atmosphere.

Or change ceramic to a porcelain or glassy type.

Bake it in a vacuum over for 6 hours at 300C.

http://www.enduroshield.com/aus/products/tile-coating.aspx

This is what you get asking for coating.

But I think you are better off baking the ceramic parts to get all moisture out.

Hire a qualified engineer that's familiar with what your trying to achieve. You'll find product reliability and safety much greater with someone there in your plant that knows what your trying to achieve.

Hang them out on the line. Tumble- drying will result in an awful racket.

Additional information on your requirements would be useful, but from what you have supplied I suggest you baking to remove existing water, followed by coating the insulator with a non-wetting dielectric such as teflon.