I love drop sets. It's the bodybuilder in me that loves the burn... I can't help it!
Usually when we use mechanical drop sets, we are changing leverage or tension somehow. I've written about a DB bench mechanical drop set by starting at an incline and slowly lowering the incline to a flat bench. You can also change the position of a row machine, or the angle of your body doing pushups, moving from hardest to easiest.
Here are some prone scarecrows that I did, which were the hardest of the 3. Then I moved to just the prone OH press, then just the rotation aspect.
Give these a try and let me know what you think!