Train for a pump.
A massive burn usually does more for shoulder development than hoisting massive weights. Achieving the best shoulder pumps occur when you increase time under tension because a contracted muscle restricts blood flow.
But since we can’t effectively wrap our shoulders to perform blood flow restriction (occluded) training sets, maximizing time under tension is the next best option. You can do this in a number of ways including drop sets, extended sets, supersets, etc.
Shoulders need a mix of everything.
Shoulders, as opposed to other muscle groups which grow via a few main compound movements and heavy lifting, need a lot of everything. Why? Because different areas of the delt respond better to different types of stimulation.
Rear delts respond best to high reps and a lot of time under tension. But to get thick, dense, and beefy front and middle delts, you’ll have to do some heavy military or behind the neck pressing.
There are two main keys to building shoulders: The first is variety (hitting different angles); the second is time under tension. The actual weight you lift here plays a secondary role when it comes to shoulders.
Focus mostly on isolation work and hit a lot of angles.
Use “growth factor” sets which combine 2-4 isolation shoulder exercises performed non-stop. What this will do is keep your delts under tension for at least a minute and up to two.
Now, there’s no doubt that bench pressing and overhead pressing heavy for lower reps can increase the size of the delts. But it tends to focus the development mostly on the anterior (front) portion of the deltoid, and the stronger this part gets, the harder it will be to fully stimulate the lateral part, which is more important if you want to look wide, because the anterior delt will always want to compensate.