The keyword for most primers is "sandable"; those are generally lacquers and easiest to work with. Most people prefer Plastikote; it's not as easy to find as Duplicolor, and most people find it easier to use than Duplicolor. You can get Plastikote at Michael's arts/crafts/hobbies stores, or use Plastikote's website to find a local store.
Zinsser B-I-N is good as a primer/sealer (sands beautifully), but it needs to be applied over at least a light coat of lacquer primer as it doesn't adhere well to bare plastic, but does to other paint.