Primer will absorb water so as a top coat it's not recommended. Primer is also softer than regular paint as it is meant to be sanded. That being said if you can not find the same colours in a regular paint you could seal the primer with and eggshell clear coat. Eggshell clear coat is like a dull clear so you wont get a shiny surface. Alot of street rodders use it to cover their satin black paint jobs.
