Okay, Carl, stop right there and pull that pony back!
I don't know how to paint in oils but Carol Williams does and she does a bang up job on horses - it just so happens that I have her book right here.
For example, she suggests a soft filbert for a mop brush. The idea of colors is to do the same thing I do with my pigments, start with a light color, work in layers and go darker gradually.
She suggests a Cat's Tongue brush for white markings, small rounds for detail such as around eyes, soft sable rounds (large) for final blending, white nylon for large amounts of body color, and the stiff bristled tapered brush for stippling.
Now, what color do you want to paint him?
Of course, you could always get some pastels or pigments and do it that way too.
ETA: If I can help anyone in any way with horsie info, please feel free to PM me if I don't see your post. Many times I'm on break or lunch at work and am in the middle of replying when I get interrupted (yes, I'm on the clock even when I'm not on the clock). When things get crazy sometimes I can't go back and finish the reply or accidentally close the tab. After that I have a hard time finding the post again because it's been marked read. Add to that I don't know the names of a lot of figures yet, so I have no idea if they have a horse or if anyone wants me to help with horses. lol!
I'm really sorry, Carl, for not responding sooner!
Cheers,
Karrie