Duplicolor's 7272 Ford Gray 500 degree engine paint in spray cans is what I assume you are using. You can go with Bill Hirsch Engine Paint (google) and get the exact correct color (which is really not been agreed upon) and then you can get pints or quarts.
What I did for my test engine, was the same thing you are doing, THEN, spray some paint in the cap and brush it on if you want. Its alot cheaper than the alternatives. On my project engine, I went with Bill Hirsch. Much better paint color. Engines require touchup from time to time.
