I often use these colors to combine the abilities and advantages of these mediums. You should work on a gessoed canvas or board, depending on the motif and preferences you can wetsand and regesso
the surface several times, using a high quality, medium absorbent material. You always work with oils on top of the acrylics!
The advantage of the acrylics is the short drying time, enabling a quick overlaying of glazes, half transparent or opaque colors to create complex structures, which would take weeks with oils. The
medium being based on water, using an airbrush is also an interesting option. Painting large areas with very smooth tonality changes, like skies, is more effectively and efficiently solved as with
oils, at least if you know how to handle an airbrush, which is definitely a more complicated tool than a standard brush.
Oil colours are drying rather slowly, depending on the mediums you can use, but usually they need a night for sufficient dryness to work on the next layer, compared to a few minutes with acrylics. I
use them for glazes and for working into wet glazes, changing and harmonizing overall tonality as well as working out fine details which need longer wet in wet working. Also oil colours or glazes
intensify the acrylics and give them a warmer touch, which is a result of the oil medium and its light refraction properties.