Best way to get a good coat with lots of shine is to feed well! Good food, linseed chips and codliver oil and as Racehorse states.......elbow grease, priceless
I find that if you have a greasey coat then put baby oil on it lifts the grease and looks awful. I tend to brush the coat. Then highlight knees, hocks, eyes, nose, anything else depending on the pony, class & markings, with baby oil on a cloth. Then run the cloth over the coat. That way you get some of the baby oil from the cloth onto the coat, without soaking it or making it look greasey.