Well, I'm not sure painting cattle will get them to stampede but it might get you kicked and scraped and bruised but hopefully not gored!
Actually, unless you are looking for a painting tutorial, I'd just google up photos of cattle - you should find large numbers of them I'd suppose - and paint to match. Somewhere in all the detritus around the house I have a book on cattle to aid in painting them - but I have larger herds than most gamers are ever likely to accumulate. Beasties, farm or wild (not fantasy) are sort of a thing with me. No, no, no, not That kind of thing! Get your mind out of that wet spot by your feet.