Several times per week my job involves hoisting 35-40 pounds of leather onto my right shoulder, then walking several yards before slinging it all onto a horse that stands 5-6' tall at the withers.
That's a pretty specific movement, and when it comes to training for specific movements, the best preparation is to try to simulate the movement as closely as possible. One way to do this is with a sandbag. Here are instructions how to do it, using sand or gravel from any pet store: https://www.youtube.com/watch?v=vpo7XyIlV_
Here's another variation: https://www.youtube.com/watch?v=QUxeiVU0tr
Then just do the movement you described. Start light (weigh the bag on a scale), then work your way up over time.
You can certainly add in a bodyweight strength program for general conditioning. Check this thread for ideas: www.sparkpeople.com/myspark/messageboard.a
Do the sandbag routine before your bodyweight exercises, so you're not too fatigued. Or do it on a different day.