How do you notify users of new features?

I am trying to add a modal to notify existing users when I add a feature. Something like this one, for example: I was thinking there was probably already a service that did this but the ones I've found have been more like a 'What's new' button or feed of blog posts (e.g., AnnounceKit) and less like a modal announcing a single feature. Do you do something like this? Is it better to just have a 'what's new' button? Do people click those? Should I just roll my own solution? If I roll my own, what is the best way to track whether a user needs to see the modal or not? Something like a lastSeenAt timestamp, or a product version? Sorry for the barrage of questions - I am mostly just interested in other people's experiences of how they solved this problem. I had the awesome opportunity to speak to one of my power users a few weeks ago and it became clear I needed to do a better job of communicating new features.