having worked out off and on for 20 years, the best advice i can give is to learn to listen to your body. some require more, some less. seems for me and many that one body part/work out is optimal. for me it's about focus. when working one part i can focus on hitting that group hard and fast. not worry about not having anything left over for next body part.
learning to listen to your body helps. sometimes i'm still sore from previous work out. like shoulders from last shoulder work out i'll skip entirely. would GUESS one part per session would be helpful especially as you have a tough job. need to train muscle deep and fast .