As a one off, to get horse home, this is what I would do.....
Allow plenty of time, chill out and enlist 3 x sensible helpers (helpers that will listen and not take over and start interferring!). open windows/jockey door, move partition to make inviting. Have hay inside and bucket of feed. As others have said calmly walk to trailer ramp, do not pull on rope, just let him wander over and just chill out, have a good sniff round, no pressure. Show horse bucket of feed so he knows its in trailer. Once horse has had a good look round and is calm enough to stand at foot of ramp, attach 2 x lunge lines to back of trailer (with 2 sensible people attached to them!!) and they should slowly walk backwards.
Timing is quite important here, but if you just ask for a 'walk on' without pulling on lead rope just as the 2 people with lines cross behind the horse so the lines wrap around his bottom he should move forwards. Important to stay calm, positive, looking forwards and not blocking the horses path and NOT pulling on rope. If he plants and his attention goes elsewhere or he tries to turn you can keep his head back facing the right direction and give a bit of vibration on the rope but pulling is likely to result in rearing. hopefully horse should walk forwards and as he does the 2 x lunge liners walk forwards with lines still wrapped around bottom until he is in trailer where they should remain blocking his exit with lines until back bar is secured.
If he really plants at the foot of ramp and the lines aren't working, you can get your 3rd person to tickle his heels with a lunge whip. And I mean tickle, not hit or poke, just cause a bit of odd sensation and they usually pick their feet up because of this at at that point a little more pressure on lines results in a slight step forwards.
This is not ideal, but it has proved successful when i've needed to use it and once you've got him home you can work on his loading.
Good luck!!