I agree with the Tamiya Primer, however at the moment it is pretty much a scarce commodity here in North America until Tamiya gets their labeling issue worked out.
A great alternative is the new Vallejo Urethane primers. I have used the grey, and liked it, just used the black primer on my Zero and LOVED it, can't say enough good things about it.
Is good to go already for airbrushing out of the bottle, and can be brush painted very nicely as well for smaller parts. Been using it lately as my go to for flat black also.....very nice!
Of course, the down side is, if you don't have an airbrush, then it can't be sprayed on, but can still be brush painted on.