There are lots of really good examples on YouTube, I never miss the Breyer horse collector type video's. Some of the painting on those horses are excellent. There is three video's in this one, however, I have given you number one.
Horses of any colour - but particularly greys - are really suited to
oil paint. The 'blendability' of the stuff comes into it's own, especially
when a 'dry brushing' technique is used to soften the contrasts.. My
tip would be to warm the darker tones with a touch of umber - it's
less stark than pure black.