I know exactly what you're talking about as of course I've seen Esprit in person and I think he's the one you struggle the most with.
Honestly I think if I had a horse with his hair texture, I'd be washing his mane, tail and forelock once or twice a week before the show with a good strong leave-in conditioner and maybe keeping them loosely braided if you could without danger of him rubbing them. Maybe wrap a strip of cotton fabric around each strand to prevent breakage? You might experiment with Frizz-Ease, I use that product on my own hair when it's being crazy before a nice night out and it works wonders.
Too much does make hair heavy and a little oiled looking but that's not a bad thing in the case of a show forelock! The night of the show I would wash the hair, condition it heavily, then loosely braid (so as not to kink it but help it smooth out) and then shove it under the slinky the direction you want it under the halter. When you take it out the next morning, do NOT comb it!
Been there, done that, it ruins the entire effort.
Just finger comb it, smooth it with more water, then gel like crazy. I bet it will look great!
I'm lucky- Kody's got great hair texture like Spyder had and Turbo's has improved with age. Last year I had to rely heavily on that bottle of conditioner as without it he was a bit frizzy and fluffy-looking. With it though the improvement was 1000%. Wash, condition, slinky, gel- boom! But God save me if I brush that mane even the tiniest bit once it's out of that slinky.
I can help you with artful forelock thinning if you want the next time I'm over. I'll trade you for you showing me how to pull a mane!
Leia