Although working with water soluble oil paints is different to working with traditional oil paints, when it comes to varnishing the same 'rules' apply. You must wait until the painting is thoroughly dry before varnishing, not just dry to the touch. Allow at least six months.
The varnish that should be used for a water soluble oil paint is the same as would be used for any traditional oil painting. Do not use varnish made for acrylic paintings.

