What is the best method to train shoulders?
Vertical pressing does hit all heads. Especially with dumbbells, when the range of motion can shift the emphasis. There are other opportunities to include shoulders – for example, when you do proper biceps curls (i.e. elbows back, no movement on the upper arm) your deltoids are actually stabilizing the upper arm. If you wanted to, say, involve some anterior delts on a biceps you could cheat your upper arms and allow the elbows to swing up, as an example.