I have just realised that the paint below can't be shipped to the USA or for that matter anywhere other than the UK. However for UK users I would recomend it.
Skytech Aircraft Etch Primer at Skycraft
This is the standard etch primer used for years in the UK and the best I have ever used.
Produced to the UK military spec DTD555.
This is real etch primer and not the "just sticks to the surface" types more generally available.
Some of the primers out there are rubbish. Ask Easyjet, when their first Boeing 737-700's were delivered they lost paint on the delivery flight and within months all the paint was peeling off the thousands of rivet heads.