Yes. It works, but my suggestion is to use low value treats (like plain hay cubes) because a really high value treat can encourage a horse to work beyond its threshold (aka, beyond the point that he’s likely to freak out). Same thing happens when you use high value treats to lure onto a trailer… you can get the horse on there, but they’ve reached too far beyond their comfort zone and will often rocket straight off the back again… you know what I mean.
To shape loading with a clicker, here’s what I would do. OP probably already knows the first few steps from Kurland’s work, but for the sake of being thorough:
First acclimate the horse to the sound of the clicker. Keep in mind that this is similar to the sound we use to teach horses to GO (clucking) so they aren’t automatically going to know it means “yay, food!”. So spend some time AWAY from the trailer just doing click/treat, click/treat, click/treat. The horse doesn’t have to do anything at this point, you’re just establishing a connection between the sound and the food.
(I would probably use the clicker to shape a few simple behaviours first so the horse gets the idea).
Then come to the trailer. Click for ANY interaction with the trailer, ie horse looks at it, horse takes a single step towards it (even if you’re still 50’ away from it) etc. Continue clicking and treating for any positive step at all from the horse, but here’s the deal: no luring him with the treats, and no dragging him up there by the lead rope. You take the time it takes for the HORSE to offer to go towards it.
Once you’re actually at the trailer, you’ll be clicking for things like sniffing the ramp, peeking inside, and (in the case of bolters) standing still at the mouth of the trailer without running backwards. You keep your rate of reinforcement very high so the horse has lots of feedback to know he’s doing the right things. If he offers to put a foot on, I would click and give a small jackpot (either a bunch of treats, or a few higher value treats) and toss them on the ground OUTSIDE of the trailer, so the horse has to step off to eat them. It seems counterintuitive, but what you’re doing is rewarding by simultaneously feeding -obviously- AND by backing off the pressure. That’s a huge reward for the horse, and gives him a LOT of feedback to tell him that he’s on the right track. He’ll be way more likely to offer putting that foot on again, and again you reward big and off the trailer. Soon it’s like the trailer becomes a magnet for that foot, he’ll be scarfing up the treats and scurrying over to put that foot back on. In the horse’s mind, he’s pressing the treat dispenser button 
Once you’ve gotten that step solid, I would raise the bar a little. One foot on the trailer means a click and a normal treat. TWO feet on the trailer is now the standard for the big reward. Then 3, then all 4, etc… keeping in mind that this may take several sessions and you may need to go backwards and start from an easier place if the horse becomes too frightened or shut down.
Once fully ON the trailer, I would be doing a very large jackpot, like a pan of grain. He gets to eat it no strings attached- no tying by the halter, no doing up the ramp or butt bar, etc. You can build on those things later, right now we’re having a party because he put 4 feet on the trailer without being coerced.
I have used modified versions of this method on my string, and I have several horses who will happily hop on the trailer and wait to be tied, with not a drop of Morgan blood in any of them 