I should first warn you that I'm kind of a home-brew solution type person, so you may not get much from my suggestions, but I'll tell you how I do it and you can take what you will from it. I tend to carry a boat-load of holders - up to 24, I like to have a selection of films on hand - when going places I really want to work on, and I keep them in a small canvas bag over my shoulder. The camera rides around on the tripod once I get setup, and then the bag goes over the shoulder for working the location.
When it comes time to developing, I use ye olde Kodak hard rubber tanks and 8 hangers at a go. I can process quite a few films in a short time with these, but it's all in the dark. Just line 'em up and work down the line. They're small enough to pack around and work in a hotel bathroom most of the time, if you don't mind working off the floor on occasion. The only drawback is the volume needed to fill them, which is a bit much for small batches but just fine for large runs.
For reloading in the field, I can say the option of last resort is a changing bag. Even the big ones don't have enough room to work, but if you get the biggest you can find, you can prop up the insides and make a sort of changing tent out of it.
- Randy