First, teach the horse the rules long before the farrier gets there.
And by rules, I don't mean the laws of a dictator. I mean the rules of a game so they can "win" in the situation.
The basic rules:
- If you stand still, it's peaceful.
- If you can stand politely on 3 legs, your foot will be returned gently to the ground.
- No kicking. That won't pay off for you.
- No pawing. That won't pay off for you.
- If you are polite, politeness is returned.
In these rules is a simple principle:
"Make desirable behavior easy and undesirable behavior difficult"
To teach a horse to stand quietly, they must be taught that standing quiet is the easiest option for them. The more they move around, the more difficult we make that behavior for them. Now, this said, I do allow weight shifting and looking around (within reason). I want the horse to be comfortable. Comfortable, not scared, nervous, restrained, or agitated. Comfortable.
A horse learns through reward, or the release. They do not learn through punishment. Very important to remember that. A dictator rules through punishment. A leader shows the way.
Now, how to stand when holding the horse...
Stand at arms length from the nose. You can reach them, they can't reach you. By doing this, you've already prevented several issues. The horse can't shake you down for treats; they can't nudge or nuzzle you; their view isn't blocked; you can see the farrier better; and you have more control.
What? I have more control the farther I am from the horse? Yes. If you are right in their face, your options are limited and have no 'leverage' with the lead line. The further away you are, the more rope you have out and the more options and control you have. If you do need to step in to grab the halter, you're only one step away anyway.
So, how do you discipline and correct a horse?
If they're trained well: only a "whisper" is necessary. Imagine a boss-mare: she controls a whole herd with only her ears. How do you get a horse to be sensitive to a "whisper"? The whisper has power because it means something. It means "shape up or else". But imagine if all you ever say is "shape up or else" but you never show them what "or else" is. You're training your horse to not respect you. (Respect. Not fear.)
We use the least amount of force as possible and as much as is necessary.
I think of "corrections" on a scale of zero through ten.
Zero obviously is no correction.
One can be a vocal "egh egh".
Two can be a wiggle of the lead line.
Three is a slightly harsh wiggle.
Four is a "I'm starting to mean it!" shake of the lead line.
...and then I'll pretty much skip all the way to level ten. Level ten is a "Oh, no you didn't! You're going to regret that, now aren't you!?"
Level ten is going to be different for every person and every horse. A very obstinate horse that will just as soon kick you as look at you, may need something more harsh. A very timid horse may not need much.
Level ten is never our goal.
Level zero is the goal.
If you only ever shout, they will never hear you whisper.
But if you only ever whisper, the whisper means nothing.
A horse that is afraid should never be punished. A horse must learn trust above all else. Never punish a scared horse.
Never hit a horse in anger. Better yet, never train a horse in anger. If you ever get angry: walk away. It doesn't even matter about ending on a good note. Put the horse away until you're calm. Nothing good happens in anger. Just walk away.
A horse doesn't learn through punishment. They learn through reward and the release.
Make desirable behavior easy.
Make undesirable behavior difficult.
Never underestimate the quiet times and the pauses in training. This alone can be a reward. This is also when a horse will think over what they just learned and hopefully stow it away in long term memory. (Music is nothing but noise without the breaks between the notes.) And besides: You're literally teaching the horse to stand quietly. Include "standing quietly" into your training.
So now that you have trained your horse and your horse knows the rules...
On the day of the appointment, you are introducing new elements that you couldn't train for: a new person, new tools, new sights and sounds, ect. Chat with your farrier. Make sure your goals align. Most importantly, let them know that if you are going to correct your horse harshly, you will tell them "Farrier, step out." "Farrier, drop the foot." If you give a harsh reprimand to your horse with a human under them, entangled in those feet; be ready to deal with a very pissed off human.
Now notice how many paragraphs deal with training your horse before the farrier arrives and how many paragraphs deal with holding the horse for the farrier.