The scouts are useless - it is far better to do the scouting yourself. I have three coaches, one scout (who I'm thinking of firing) and three physios.
Good leagues to hunt for staff in:
The small leagues with only one human player managing. People rarely look there, and there are often really good coaches to be found. Israel was particularly good if I remember correctly.
If you find you players are completely knackered (=tired), get them in a training session involving fitness training at medium intensity.
Training intensities have a trade-off with stamina. As you'd expect, better results are observed at high intensity, but your player will see a hit in stamina as a result. Less stamina means your player does not play very well and is more prone to injuries.
I guess I'm stating the blatantly obvious, but good luck!
