Im sure you have in a stall with you. So get in that stall with him and a long show stick. Walk behind him, he will naturally go to the edge of the stall and come to stop at a certain place in the stall. If he does not want to move use the stick to get him moving. Once you and him have determined his happy spot in the stall walk him another rotation and when he gets to that spot, use the show stick to rub his back, belly, rump, legs and pretty much anywhere he will let you. You will be able to see it when he has had enough or is annoyed by the attention. So, just make another ration in the stall and continue rubbing him with the show stick.
Gradually this animal will start to trust you and so move in a little every time continually rubbing him, and you will find out which spots it likes and dislikes as mentioned earlier. Continue to do this until the animal lets you brush him, as you brush him please steer clear of the head. I like to not touch my animals heads as i feel this can lead to the animal thinking it is play time and wanting to head but or play charge with that head down. So the Neck is where i tell kids to rub, not the head. Now that you and your animal has gained enough trust in each other through stick rubbing and constant brushing, it is time to introduce the halter, i like to gradually introduce the halter first by just hanging it over my should so the animal is aware of the new object in its space. Then through my brushing, i slowly rub the halter on the animal. I continue with this every day First sticking, then brushing , then rubbing with the halter this will gradually calm down any animal that has ever been put in my barn. Only after all this do i put the halter on, but im not just gonna put the halter on and leave it tied up for hours right off the bat. When i get their halter on i continue with the stick rubbing, and brushing all with the halter in my hand. Remember these animals have to trust you before they will follow you.
Of course when something new comes into the barn i like to feed it for two or three weeks before i even mess with it.This gives the animal time adjust to its new surroundings, and lets it understand that it is depending on you for food and water.