I mount the riders and horses separately on cardboard to allow for easy handling without paint rubbing off. I almost always paint horses and riders separately. This does mean touching up the boots or shoes of the riders once they are pried off their temporary bases but I find that easier than trying to paint around the legs if they are in the saddle from the start
I then spray with a white undercoat. When that is dry I apply a light wash of raw umber over everything.
This photo shows the horses and riders after the wash has dried.
The horses are painted with a base coat which I apply thinned with water so as to bring out the detail.
I will be painting (from left to right) a Grey, a Chestnut, a Bays, a Black, another Bay and a Dun.
The Grey gets no base coat. If it was going to be a White I would highlight the raised areas with pure white. The Chestnut and first Bay get a light red-brown base coat. I use Wacofin N Rehbraun (fawn) which is probably the most useful colour for horses as well as being an excellent mix with pure red to give a deep brick red colour for clothing.
The Black and the second Bay are painted with dark brown and the dun gets a light sandy brown. Blacks are never really truly black. There is almost always a tinge of brown which comes out especially in sunlight.
Each horse now gets a wash over the base coat. This will change the colour quite considerably. It is a good idea to play around with different washes over the same base coats to get variety.
Coat d'arms various ink washes are excellent, giving a nice gloss and depth of colour over the base coat. For the Grey. however I used Liquitex Mars Black as it is much more translucent than the Coat d'arms paints and I do not want the horse to become too black. For the others the washes used are (from right to left) Coat d'arms Chestnut, Brown, Black, Brown and Flesh ink washes.
You can see the difference made by using a different wash over the two horses originally painted red-brown and dark brown.