Yes, you can apply TotalBoat Elixir water-based enamel paint directly to a cured epoxy surface, as long as the surface has been allowed to cure under normal temperature conditions for at least 5-7 days.
To prepare the surface, remove amine blush, if present, by washing the surface with a mild soap and warm water, rinse with fresh water, and dry completely. Remove any other surface contaminants such as dust, oil, and grease, by wiping the surface with a lint-free cheesecloth or clean cotton rag dampened with denatured alcohol. Sand the surface smooth with 320-grit sandpaper. Wipe clean with denatured alcohol and allow to dry completely. Apply TotalBoat Elixir, as directed.