It will take quite a few spurts to accomplish this. Each time his tail will raise and lower in a brief flick. The first few jets are of a thin to average consistency of cum. You can easily drink cups of it with no discomfort. The Mare - how to do it.
Mares can be quite satisfactory for the average well endowed male.
If you are somewhat less developed you might find better pleasure with a pony or Miniature Horse. These are also better as they are lower to the ground. A pony you can fuck standing up. A miniature horse on your knees or squatting depending on the size. Fucking any horse will depend on the horse.