I spent a couple of years playing missionary. There is no such thing as missionary flying, any more than there is bank check flying vs. flying video tapes.
"Missionary" flying often does involve back country work or bush work, most of which is strictly common sense flying. I know that several other posters here have also done this type of flying (Turbo, jump in). It can be demanding, or may not be. It may involve operating with few navaids and unpredictable weather with little forecasting or reporting available.
Plenty of places exist right here in this country (USA) where you can find this type of flying, and get some feel for what it's like. You can head up North and get an idea.
Personally right now, I'd be trying to avoid these types of overseas operations, if I were you. Otherwise, get an agency with good kidnap insurance, and plan on staying single for a while. Good luck!