More thoughts on paint versus dyes:
I have never painted leather with acrylic paints, so I may be mistaken about this, but my assumption is that the acrylic sits on the surface of the leather, and diminishes it's capacity to absorb water. Dyes, on the other hand, are absorbed into the veggie tanned, and do not inhibit water absorption. I airbrush the dye through a stencil with the leather flat on a table, after cutting it out and before shaping it. Can you do that with acrylics?
I learned airbrushing many years ago spraying acrylic paints. What a pain. The acrylics dry so quickly that the airbrush needed constant cleaning and I had to work fast so that it kept spraying. Once I switched to solvent based paints I discovered how much easier they were to airbrush due to the slower drying time.
The dyes I use are made by Special-T http://www.specialtycoatingschem.com/
They are the PSTF dyes, and come in many colors. You can buy just the primaries and mix them. I would like to hear others weigh in on this topic. Thanks,