primer

I use MM grey primer as well. Works great, goes on smooth and prevents lifting when you mask. MM paint is always 'thin'. Not to worry...

Andy

This is a somewhat complicated subject, which lots of people seem to misunderstand.

Primer, in general, has several functions.  1. It seals or otherwise prepares the surface, making it receptive to the finish coat.  2.  It makes it physically possible for the finish coat to stick to the surface, and stay there.  3.  It makes the object to be painted a uniform color, so the finish coat doesn't need to be too thick.  4.  It provides a smooth, even surface that makes application of the finish coat easier.

Some of those functions are relevant on some surfaces and some aren't.  Some surfaces (e.g., soft woods) need priming and filling to make them smooth.  Some paints don't stick well to some bare surfaces (e.g., metal).  Neither of those considerations really applies to styrene plastic.  Modern hobby paints are formulated specifically to stick to it.  (People who think they're making enamel paint stick better to plastic by putting a "primer coat" of the same kind of paint on first are kidding themselves.)  Nos. 3 and 4, however, are sometimes applicable to plastic kits.  If the kit is molded in more than one color, or has some filler of a different color applied to it, several finish coats may be necessary to hide the differences; a coat of neutral grey primer may be useful in reducing the total number of coats to a minimum.  And brush painters, in particular, often have trouble covering a large area of dark-colored plastic with light colored paint - especially if the plastic is shiny.  A sprayed coat of flat grey will provide a good base for a brushed finish in just about any color.

If either of those considerations is what's leading you to think in terms of priming the model, the definition of a good primer is just about the same as the definition of a good finish coat.  You want it to be a flat, neutral color in a consistency that covers the surface easily (preferably in one coat) and provides a good base for the finished color.  If a particular paint seems too thin or too thick - it is.

I do a fair amount of brush painting with acrylics on ship models, and I find that a careful spray from an aerosal can of a light or medium grey enamel (e.g., Testor's Model Master)makes a good primer - when I need it.  Most of the time, though, I don't bother with a primer at all.  I've got a couple of models I painted with acrylics (and no primer) more than 25 years ago; none of the paint on them shows any sign of coming loose. 

Wood and metal, of course, require different approaches.   

I've always had good luck with floquil primer, however I am looking for a good acrylic alternative.

 Rod

But do you think it will help if I don't thin it as much as I do to paint?

Thanks for the information!

I'm using regular, run-of-the-mill krylon primer from the auto parts store (or maybe it's dupli-color; I use both).

It works great, I don't have to clean the airbrush and it's cheap.  A large can costs less than a small bottle of the other stuff.

I too, bought into the whole "it has to be made for airbrushing" thing, but sometimes, you just have to know when the companies are just trying to make a few extra bucks off of you.

-Fred

I've been using the 96 cent a can gray primer from Walmart.

I like to use flat light grey enamels....whatever I happen to have lyin' around at the time.