I went through this on friday, I'd been doing it out of my maintenance trailer, and then I did it out of the dump.
My dump is level with the height of my wheel barrow, so instead of getting a shovel full and lifting it in, you grab a big shovel full or just scoop and slide it across the floor of the dump trailer and into the wheelbarrow. There isn't any lifting.
I figured that I could load a wheelbarrow twice as fast as I could when I lifted it, and when it runs out near the gates of the dump, you lift it and slide all the mulch to the back.
With that said, I had to do it at a large resi and it kinda sucked bringing the heavy dump into the field and out back.
It all sounds dumb, but I was surprised how much difference it made.