Enamel primer and acryl

Primers won't make acrylics (or any other kind of paint) cover any better or worse, that isn't their job.   How the paint is sprayed or brushed determined how it covers, although the color underneath may make it seem like it covers differently (spray white paint over white plastic sometime).  Primers adhere to styrene better than most other paints and in turn most other paints adhere to primer better than they do to bare styrene.  This is very important when using acrylics since their adhesion isn't as strong as enamel or laquer to begin with.

As to staying tacky for some time, while acrylics do normally dry very quickly there are several things that could cause them to remain tacky.  High levels of humidity in the air or spraying them over an uncured base are the two most common.  Sometimes they just seem to stay tacky because they feel like and no other reason.  You didn't say what (if anything) you used to thin the acrylic with, and some brand-name acrylic thinners contain retarders to slow down the drying time.  Retarders are normally a good thing since acrylics dry much to fast without something to slow down the drying time.

exactly musicCity

hey Scott and welcome aboard!  Quick question, how long did you let the primer dry?  I've used the Testors Grey primer and it seemed like it took a bit to cure good.  Longer than the krylong primer I have used ever since.  Maybe your primer wasn't cured?

Typically for MM Acryl it takes about 10 to 15 min to be dry, 24 hours maybe more till I feel safe it is cured.

The other question was raised before, what did you use to thin it with?

I gave the primer 24 hours to dry and I didn't thin the Acryl. I just brushed both on some scrap plastic. 

ahhhh.. I just thought of something.... you might need to thin the acryl a bit and use several thinned coats to paint it until it is covered.  I was thinking airbrushed and airbrushing leaves a much thinner coat on the plastic than brush painting.  Maybe it needed some more time... thin it and put it on some scrap and see how fast it dries.  You might need to put it on in several coats waiting in between for it to dry...

MM can even be thinned with alcohol, although I like the way it settles down with Tamiya thinner or an Acrylic retarder (also called airbush medium)

Thanks for the advice.