I think I would approach trailering in the same way for both horses. The difference will be in how long it takes each one to gain confidence. I'll break the basic pattern I follow into steps as best I can.
Step 1: Approach trailer with horse. Be purposeful here, expect the horse to calmly walk aboard without breaking gait. Walk purposefully up to the open trailer, looking straight where you're going. Think of it as setting an example for the horse; you want him to focus on the trailer and step calmly on, too.
Step 2: Allow the horse to become confident at the edge of his comfort zone. Depending on the horse, the edge can be a variety of places. You will know the edge when the horse requires further encouragement to go willingly forward. Instead of pulling and getting into a tug-of-war, just stop and allow the horse to "observe" the trailer. A dry lot is best for this step, since many horses will try to graze. Don't let them, if he's grazing, he isn't learning about the trailer. Don't hold him at the edge, either. If he feels the need to back away, allow 2 voluntary steps back, then start backing him up. Back until your horse begins losing the "run back" midset, then immediately reapproach (ALWAYS face the trailer), and allow him to rest at the edge of his comfort zone. Depending on the horse (especially with a more fearful horse) I might dispense treats here. The treats are not meant to "bribe" the horse onto the trailer (ie, luring them on, "here, horsie horsie..."), but to facilitate relaxation and stimulate the "lickey, chewy" mouth of a thinking, relaxed horse.
Step 3: Reapproach. When you have several of the relaxation earmarks (lowering head, licking and chewing, resting of hind leg, relaxed tail, blinking, desire to graze, etc.) ask for the horse to step closer. When you encounter resistence again, allow the horse to relax as in Step 2.
Phase 2 (In the trailer).
Step 4: Allow the horse to relax in the trailer. Don't hold him in or tie him, simply expect him to stand on a loose lead. Praise, treat, pet, as applicable to the specific horse. If the horse chooses to back out, allow him to unload himself uninhibited until his hind feet are on the ground, then start backing him up and away from the trailer (as in Step 2). Again, keep facing the trailer. Reapproach and allow rest and relaxation in the trailer (or as close to it as possible, some horses take a few "dry runs" to digest what just happened before a second loading).
Tips: Don't get excited, this is not a big deal. If you make it into one, the horse will think it is. It's no different than leading the horse into his stall or pasture.
Wear gloves and use a long rope or lungeline (if you are confident handling that big of a rope coil in a hurry, if necessary) if you are concerned about a horse running back. If they learn how to get away to release the pressure, that can quickly become a dangerous habit. Keep his eyes on you, and maintain your "personal bubble" until the horse is confident. Perhaps invest in a head bumper if the horse is throwing her head up inside, the last thing you want is for her to associate the trailer with pain.
Practice obedient leading without a trailer. Often, when it comes down to it, problems loading are problems leading. The trailer is just enough of a stressor to the horse to bring out any bad leading habits he may have.
If at any time you feel that the situation has become unsafe, please get on-site, professional help.
I hope that was a bit helpful for you. I'm no professional, but that method has gotten me through (relatively) minor issues with my own horses, as well as a few others, with minimal fuss.
EDIT: Barrelracer's CA version works well, too. I actually like it a little better as far as speed of effect, but I ended up tweaking mine to the above version when I was dealing with an older gelding who knew how to rip away from a handler if he got too flustered, and got easily flustered with lunging.