For what exercises should I use dumb bells versus machines or a barbell?
You can use dumb bells for basically every muscle in your body. As far as preference, I think using dumbbells for front and side shoulder raises are really good and also rear deltoids flys. Dumbbell shoulder training is good because your shoulder muscles work as stabilizers when you’re doing lifts like “bench presses”. I think dumbbells are good for doing upright rows instead of barbells because barbells seem because you have more free range of motion. Another exercise I prefer would be standing dumbbell curls. I hear some people in the gym complain about pain in their forearms when they start going heavy with barbell curls. Again, I think dumbbells allow more free range, so you don’t get the same pain in your forearms.