I read some of these suggestions and I realize the halter world hasn't changed in decades. I haven't seriously shown halter horses since the late 80's and didn't even know Pepi was still on the market!! lol.
I'll chime in here since 'natural' is all I do. I'm all for a more natural look! That's all I'm used to @ stock horse shows, reinings, cuttings etc. (where there is always dust being kicked up and all that oil and product...ick..makes a horse ugly quick, especially if they sweat any.)I like to keep them pretty bare of products on show day, a nice groom job will go a long way, start with the rough brushes (curry &stiff) and work your way to the soft brushes and rags. On show days I go all out and use every type of brush in my arsenal to pull out the natural shine. I also do a lot more prep work at home over the long term. Making sure they're fed and groomed regularly etc. and my horses usualy look great on show day. There really is nothing like elbow grease on a healthy horse. For a little help, I like to use a little Vetrolin Shine (you'd be surprised at how little I put on a big horse) on their mane, tail, hip and shoulders just after a bath while they're still wet, let 'em dry then groom to the max. I also keep an extra set of brushes that I keep super clean just for show day. Brushing a clean horse with a dirty brush on a show day...well it's useless. If I do all this, I usually just have to wipe the dust off of them with a soft cloth as needed before each class. Clean always attracts less dust than Pepi or any of the other sprays I've used. Dirty dulls. I do use the Vetrolin Shine pretty regularly anyway because it has a sunscreen in it and my big horses are always turned out so it keeps the hair from fading and drying out (and we have a hot intense sun here, fading is already starting to happen with my non show horses that I don't waste the product on!) So for a long term maintenance, it keeps the hair always looking healthy and nice and is awesome for keeping a tail nice and tangle free on a regular basis. I haven't seen it give any problems under tack but it is a silicone product so I also don't use it in the critical areas such as where the saddles and girth sit. Also, for braids I wouldn't recommend it or any oil based products, too slippery. 'dirty' manes are usually easier to braid. Dried hairspray (don't bother trying while it's still wet) is sometimes is good for braiding too. Once it's dry it gives the hair a little tacky feeling that will help the braid. cheap ones usualy work best, lol. The expensive 'natural' feel ones are too soft.
A decent ph balanced shampoo will also benefit the natural look and leave them with a nice shine on show day. You don't want to strip the natural oils on show day or any day for that matter....I like the Jeffer's shampoos, particularly the citronella one. It's been great for me.
For hooves, IF we do anything, we still use shoe polish and hairspray vs hoof shine that you have to remove, it's very easy to apply and easy to touch up as needed as well as it just hoses right off.
A week before the show I also like to give 'em an olive oil treatment, I put olive oil in the mane and tail and let it soak for at least a half hour (usually longer) then wash it out, rinsing well. If it's really dry hair, I might do a few of these treatments over the course of several weeks, but this is all in advance of the actual show day. I wouldn't recommend all that oil on show day, just attacks dirt and leaves 'em full of grime. oh! I have a friend who says braiding with olive oil in the mane is the best way to train manes but I haven't tried it yet. To be honest, I just remembered she said that...I think I'll be giving it a try since my little guy has zebra/donkey mane going on right now. olive oil is also great for curly hair, that want so cord into witches knots! I use it when I want to straighten my own hair, I put olive oil on before my shower on the mornings I want to straighten it, wash it out, then after I blow dry it I just have to touch it up with a flat iron and trust me I have curls in my hair! enough that all it takes is a little gel to get the curly look to come out perfect.
For stock horses, we will give them the tiniest bridle path, just about the length of my thumb which is probably around 2 inches, maybe 2.5 at the longest. Just enough to be able to place the bridle without the mane interfering. Gives a very clean but still natural look. I am trying to convince myself to give the mini's longer bridle paths to show off their neck but it's going against my grain at the moment! Again, with stock horses for the more natural appearance, we cleanup the ears but not all the way in the ear like a halter horse. I usually don't even clip, just take a pair of shears, fold the ear & trim the excess along the ear (this can be done with a clipper too, for speed) then take a pair of thinning shears and clean out some of the extra fuzz that might make them look like a fuzzy bear or might collect wax and dirt. They still have plenty of hair left for bug protection but it looks a lot cleaner that if they were just pulled out the pasture. I usually maintain that all year anyway so this is not a big deal for me on show days. Rarely, if ever, will I shave the whiskers, sometimes we'll clip off the excessively long ones, if the horse is just extremely hairy or the hair color contrasts strongly but most of the time I don't even touch it. I honestly don't think it detracts from them that much in a performance class but that's just me.
I will however clip hairy legs, sometimes even in winter (I have a very warm, wet climate, so it's mostly for health reasons as mud and hair usually leads to nasty.) Give the hair at least a week to grow back in especially if you're not experienced with a set of clippers.
Most of my show day grooming is pretty simple and I try to get most of it done well ahead of time. It's also less stress on me and the horse! Since I do so much prep grooming (I seriously groom in some form every time they come in the barn) they're very used to the routine and just settle in for the duration. It helps calm us both down.