I've been using this extension called "Crackbook Revival" which allows you to set timers upon visiting certain websites, in a certain time range like 9-5. I have it setup on Reddit and Youtube to do a 10 second delay before loading the webpage.

I think one of the important tricks to using friction productively is to not use it too aggressively. A lot of people get started on this idea, but they almost instantly find themselves turning the friction back off because it's too much. For example, staying logged out of every website all of the time sounds like way too much friction for me, but Crackbook works because if I really want to watch a Youtube video, waiting 10 seconds really isn't all that long.

More research on what types of friction work, and what types of friction don't work would be extremely useful.