Injection molded plastic - base coat/s before LAQUAR paint

I have used both Tamiya and Mr. Surfacer with great success for both.  Mr. Surface has the advantage of coming in various grades of "fineness" for you super fussy guys out there.  I find Mr. Surfacer "1200" in a rattle can works just fine.  You can also buy it as a thick liquid in a jar, which allows you to fill gaps with a small brush or toothpick, or you can thin it and run it through your airbrush.

Frist off to the forum!

There are plenty of laquers that you can use.  I usually prime everything with Tamiya's fine grey primer which is laquer based I believe.  If you're concerned whether or not a specific paint will attack the plastic my best advice is to try it out on a scrap piece before applying to your project.  If it looks good and doesn't attack your scrap, then it should be good to go.  I would still recommend going slowly and applying only light coats just to be safe. 

like I said, I use Tamiya's fine grey primer (rattlecan) since I like the way it covers.  it may be hard to find though.  I've just started using Mr. Surfacer as a primer and have to say, i'm impressed so far.

hope it helps!