Ok first I get a base - obviously lol
Then I search on DeviantArt or google for a horse in a similar pose, like this for example
Then I use this tool, it's called the eyedropper tool
And start putting the colours on from the photo like that. If you don't know how to use the eyedropper tool, just open your photo in a different tab, click on the part of the horse you want the colour from, and it automatically selects that exact colour, then paint it on your base!
Now just smudge it all together on strength 26%
Then I search on DeviantArt or google for a horse in a similar pose, like this for example
Then I use this tool, it's called the eyedropper tool
And start putting the colours on from the photo like that. If you don't know how to use the eyedropper tool, just open your photo in a different tab, click on the part of the horse you want the colour from, and it automatically selects that exact colour, then paint it on your base!
Now just smudge it all together on strength 26%