protective coating

Maxwell wrote:

But acrylics to me are fragile and can't take much handling and I want my models to last. In this sense enamel is better since it has a more durable finish.

That isn't necessarily the case. Tamiya and PollyScale acrylics, properly applied and cured, are very durable. I have even  used both to paint camoflage on my hunting bow—and it gets a lot more wear and tear than any scale model! I routinely use Tamiya acrylic as a primer.

There are two keys to acrylic paint adhesion:

• An absolutely clean surface to which they are applied.

• Thorough curing. 

 Clean the surface of your model with detergent and water, Simple Green (rinse thoroughly!) or a surfactant cleaner like Formula 409 or, better yet, Windex. Do not handle the model with your bare fingers from this point on. Follow with an isopropyl alcohol (90%), ethanol, or denatured alcohol wipe or rinse. Allow to dry in a dust free place.

Acrylic paints appear to dry relatively rapidly. Don't be fooled. Drying is not the same as curing. Allow the paint to cure for at least overnight (a full 24 hours is better, especially if it's humid). You can accelerate this process with mild warmth and air circulation. (Place a 60 watt lamp in front of a small fan blowing on the model after it is dry to touch.)

One other thing: Thin (reduce) Tamiya paints either with Tamiya thinner or 90 percent isopropyl alcohol ONLY. 

Triarius is exactly right.  I use Tamiya Acrylics exclusively.  Make sure the plastic parts are totally clean and devoid of all oils (such as finger oils).  Primer your parts with Tamiya primer, make sure it's fully cured (like Triarius said, drying and curing are two totally different things... patience really pays of with this ). 

After you paint, wait until the paint is fully cured, then seal with a clear coat, such as Future (which is nothing more than clear acrylic).  If you want a flat finish, mix some Tamiya Flat Base with the future (4 to 1 is about a concentrated as you'll want to go with the flat base, for a more semi-gloss or eggshell finish, use more future to flat base like 6 to one or even more).

As long as you handle the model properly, you'll have a nice durable finish.