Hi Porshaa, how funny, I used that top appaloosa as a reference for this guy.
Just as Robyn said above, install as many moveable appaloosa spot markings as you can and then for this guy, I literally just used layer after layer of different markings i've downloaded to get the look I was after. Sometimes you need to mess around with the opacity button for each layer in CAS as well as changing the base coat and marking colour's.
I am literally attempting another appaloosa coat for my friesian appaloosa sport horse foal, so if it's a success, i'll see what other's think and will attempt more for people to download if they like. (I am very much a beginner, I find merging public content so much easier for getting an appaloosa coat done rather than making one!)
Good luck with yours too