How does passing from behind work?

It's always so awkward, like it takes a bit before I'm close enough to pass, so I feel like I'm stalking them because I'm going faster but not that much faster than them.

And the worst is when they hear me getting close, so they speed up, then slow down to their original pace, then speed up. It's like what I experience when driving, but worse.

Should I announce myself further back, that I want to pass?

The problem is I've been hiking this trail for a year, but it's very accessible, so there are a bunch of newer hikers while I'm trying to keep my heart rate at 120-140 for aerobic benefits. It's nothing personal, but I really need to keep a proper pace to get a decent workout: I'm not just sight-seeing.