Every time he is lazy, disrespectful, pushy, dangerous or whatever you work his bum until he is about to drop dead or pass out.
No 'hate mail' from me but I will tell you why I disagree with this theory...
First I do agree that we must give *consistent & effective* consequences & sometimes this means punishment. Horses, thinking like horses, need *instant* consequences, in order to link the 'crime' with the punishment(or Right behaviour with reward for that matter). They cannot associate 'causes' abstracted by more than a few seconds, with 'effects'. That means that if you cant punish(or reward) a horse instantly, then don't bother.
It also means that the horse 'forgets' why he's being punished very quickly after he stops doing it, if the punishment continues, it will only be associated with whatever IS happening at the time. Namely, 'working' him in this case.
I want to do all I can to ensure my horses enjoy my company & their 'job' as much as I do. I absolutely don't want them thinking 'work' is punishment. I strive to get them thinking of it as (controlled) play! They also get rewarded for 'good' stuff frequently.
I also think it's vital to really consider the horse's motivation for 'bad' behaviour like this. Try to understand the *cause* & address that rather than just punishing him for it. He is trying to tell you something. Maybe the saddle or something is hurting? Is he bored, frustrated, stressed?
Now back to op...
One other thing with punishment is, especially if you give no thought to the motivation for his behaviour, or his personality, you could end up with a horse that 'ups the ante' when you do & he could get(more) seriously dangerous.
Punishment must be strong enough to be *effective*, to have the desired effect of causing him to be reluctant to 'earn' it again. For some horses & situations that may be... quite hefty.
If you swat him on the nose for biting & he thinks it's a game, that's far from effective punishment. Sounds more like a reward/play & that that's the way he saw it. So it's actually encouraged that behaviour.
And on the flip side of 'positive punishment' is positive reinforcement/reward. If instead of focussing on punishing him for 'bad' things, you teach & reward him for 'good' behaviour, you'll find the need for punishment greatly reduced too. Especially if you teach him behaviours that are mutually exclusive to biting etc. If he's being rewarded for keeping his nose to himself then he can't be doing that while snaking it out to bite you...