I've always used model master and testor enamels for my models, no primer, no acylics. I always thought acrylic is for paper not plastic. Am I wrong?

In a word, yes. There are several acrylic model paints(Lifecolor, Vallejo, Tamiya, Humbrol, Model Master, etc.). Tamiya, individually, is made to use in an airbrush. You will find a lot wider range of colors by using acrylics.

Well you're wrong about acrylic being just for paper

As for which paint you use it's a matter of which works better for you. If model master and testor enamels work for you and you have a ready supply of them then why change.

I use acrylics, enamels and oils for more models

okay so what would I use oils for? and then enamels? I'm so confused

First of all, be sure to read what the paints are intended for, as there are some acrylics that would not be applicable to plastic models.
There are two main types of paints used for plastic models at this time; acrylics and enamels. Acrylics have mainly been developed because they are safer to use than enamels. I do not recommended that you try to mix different brands of acrylics unless you have a lot of knowledge about them. In other words, use Testors thinners with Testors paints, Tamiya thinnners with Tamiya paints, etc. Also, do not try to mix acrylics with enamels; it won't work
Acrylics tend to dry faster and harder than enamels, which makes them easier to apply washes and filters. They sometimes do not adhere as well to plastic, so some brands work better over a primer to avoid masking tape lifting paint off of the painted surface.
Usually, you can use acrylics anywhere you would use enamels. Acrylics can often be washed up with simple soap and water, and some can be thinned with water or alcohol.
Oils are usually used for washes and special shading effects. They tend to work best over acrylics because the oil paint thinners will not affect the dried acrylics.
I would suggest that you purchase one or more of numerous publications about painting, as it will get way too involved to fully cover here.
Norm Samuelson

okay, thanks yall!

What I would say is that Acrylics dry faster than enamels but are not as hard setting or durable, which differs from what somebody has already said on this thread. Enamels are harder to work with because you need to work with thinners and they take longer to dry, but do, in my opinion, give better results.