In september 2008, I attended a course in painting with acrylics at the KunstFabrik Wien, in Vienna, Austria (their website). It was a solid 5 days of painting, instructed by an active professional artist named Erwin Kastner (his website).
The course was not cheap, (around 430 Euros) but the factilities were exceptionally good, and the instruction was quite fine and professional. And, it was a solid 5 days, nine till five.
I had somehow had the idea that acrylic paint could not be used in all "serious art" applications, but Kastner quickly rectified that view. He demonstrated the use of acrylic paint in three different techniques: as aquarelles, with spatula, and traditional painting with brush.
Here, Prof. Kastner is demonstrating the very wet aquarelle style, with highly diluted acrylic paint. The main difference between this use, and regular aquarelle colors is that once acrylic paint dries on the paper, you can't get it off again. So no "lifting" or "erasing" is possible.
I didn't have much success in adopting this technique. I have trouble distinguishing between artistic freedom and sloppiness, and this, for some reason, is most manifested in the very wet aquarelle style painting.
I don't want to use his own demonstration piece here, who knows what copyright issues might ensue, so I put up one of my own, done at the course. ("Fruit", on paper, 65 x 70 cm.)
For the spatula applications, he actually used plastic cards, similar in size to a credit card, but made of softer plastic. These produce nice broad strokes of color, when you want, and do not scrape the paper or canvas, as one is more likely to do with the traditional metal spatulas with handles on.
(One fine day, I will figure out how to color-balance digital pictures for display on the web.)
For this purpose, the relatively cheap, liquid acrylic paint is ideal, pliable and opaque. Indeed, the other participants in the course had brought half- or one litre bottles of each color, or even a 5kg bucket of white.
Finally, the paint can be used (almost) like the traditional oil colors. I say "almost", as I find, as an amateur without much experience, that one needs to worry a little more about the state of the paint and the brushes. The paint dries up in a few minutes, unless one sprays it with water, mixes retardant, or whatnot, and the brushes may dry out in your (my!) hands.
Here the instructor is showing me some fine point, or maybe just telling me to give it up.
A benefit, though, of using the acrylic paint instead of oils, is that the solvent is water (and a little soap, sometimes), and this isn't hazardous, and doesn't stink.