Primer

After switching to Tamiya acrylics seveal years ago, tend to use an oil-based enamel.  Regular brands are Krylon gray primer and Testors gray primer.  Why not an acrylic primer?  Enamels chemically bite the styrene and creates a tough platform that will be far less likey to pull away after subsequent color coats are applied.  Acrylics simply don't share this quality.  This is just my preference, others will have serveral variations.

I use any of the modeling light colored flats for my primer needs. Other sources of primer such as the ones for automotive (I have used Krylon Fusion) that are non reactive with the plastic. Some primers will craze the plastic and ruin a good model. You just need to read the labels and test it first...labels can be wrong.