I use a Paasche VL (double-action, siphon-fed), running on a Craftsman 1.5 hp compressor with a 3-gallon tank. I use this on my scale models; I haven't yet tried it on small figures, though I am experimenting with it on larger-scale resin figures, like a 1/6 scale anime figure.
I run Tamiya acrylics through it, thinned with Tamiya's proprietary acrylic thinner (a combination I also use when hand-brushing Tamiya acrylics); Model Master paints-acrylics thinned with isopropyl and enamels thinned with mineral spirits; Testor's enamels, thinned with mineral spirits; and other acrylics, such as Andrea, Vallejo (not their airbrush paints) or craft store acrylics, all thinned with water or with isopropyl, depending on what I feel like.
I have also airbrushed matte Tamiya acrylics thinned with lacquer thinner, because that produces an absolutely dead-flat matte finish, even better than using them with the proprietary thinner. Sometimes I prefer that finish.
I generally thin the paints to a 50/50 ratio, and my usual pressure is around 20 psi.
Hope that helps!
Prost!
Brad