Trifolding it shouldn't be bulky at all (that's what you're doing). That really is the trimmest way to go, actually. Remember, it's never going to be as trim as a paper diaper, but it's not too bulky that way. If you're having to fold down a lot of excess, you may need smaller diapers.
For Camille, I would actually fold them the other way. Instead of folding them along the natural seams with the padded part taking up all of the middle, fold it against the seams so that the padded part folds over on itself and is in the center of the diaper. That way, the middle of your diaper will be thicker than the top or bottom. You can do this with Jackson if he is a light wetter, but it works better for girls than boys. That will also make your diapers shorter, so no excess to fold over.
You could try twisting them, but that's fairly bulky between the legs.
I'd do what you're doing!