I only paint one side of the flats .. the side seen when set in a frame. Most dioramas seen from one side require not more than one side painted. The other side is usually painted in matte black (acrylic) to prevent any shiny spot or brillance from the edge.
Many people are painting wih oil colours, but Spanish painters are more likely using acrylics, and mastering this painting ver, very well. Advantage is also that the paint is drying very fast.
I swithched from acrylic to oil, nice to handle, but long drying tiles, and colour shifteing when blending colours in the days after wet painting ....
It is a matter of habit, and expérience from before, or club/school on learning the technics...
I undercoat large flats with coloured acrylic painting on the primary layer (acrylic clear tone or Hymbrol double diluted layers) to pre-colour the flat and so reduce the amount of oil needed after (quicker drying too), or for glazings with oil . For small flats, directly oil, the firt layer slightly delited with turpentine of white spirit...( to have quicker drying for next layer and respect the fat on mager rule.
