Primer is good for providing a uniform, paint friendly surface prior to airbrushing/ brush painting.

I recommend Tamiya primer for priming detailed parts. It is expensive but it is highly atomised (fine) and will not smother intricate detail.

A tip for using primer. After shaking, submerge the can in warm water. This will increase pressurisation and thus increase atomisation.

Automotive primer is available from most hardware stores, but some brands are very thick and tend to smother detail.

Chas