LOL, I feel your pain, I am also on my own teaching my guys to load, and it has been a struggle, mainly because once a horse has your number it is very difficult to change their minds, as you say she cocks a leg and looks at you and says "really" because you have tried and quit and now she has learned that if she holds out, you will give up. Don't worry I was in that place as well, and it is going to be a battle but you can turn it around again, but you must set aside a whole day if needed so you can work on it until you win.
Those videos that aerie posted are totally excellent, and definitely start with them. I started with getting my mare to move away from the tapping properly, and sending her in and out of a door way before even trying it at the trailer, one mare, this worked like a charm, and I always load her this way.
For Ben it worked a couple of times, then he learned to swing his butt away from me and resist, he is also so tall that he was making my arm ache keeping tapping him on the butt, so I progressed to a butt rope
That allowed me to control his back end, while still tapping, or I would get on the trailer and use the halter and the butt rope to bring him on after me.
Then that stopped working and a very nice cowboy took him off of me at the arena one day and did the whole lunging and sending on thing, it took him an hour, but it worked, and it continues to work again and again. I wasn't a believer before, but now I am!