Wave cars through when it’s safe. If I can see around a corner before the car behind me can, I’ll give them a big wave to come around when it’s safe to do so. Usually, they really appreciate the “teamwork”.
I’ve had the opportunity to safely catch-up with some people on the bike outside, and have heard one line of questioning more than any other: “What are you training for? Are there gonna be races this year? What’s been motivating you?”