When traffic volume permits it, herd the beasts. Yesterday I swung into the traffic lane as soon as I saw how things were shaping up. This blocked the drivers behind me, forcing them to slow down sufficiently to let the oncoming motorists come through. The instant the oncoming motorists had cleared, I snapped back to the right to release the overtaking set.I do have a few points of clarification, however. Instead of swinging into the traffic lane, it's often more expedient to already be there, taking the lane by default, a method I will expound and promote in this blog, and then moving aside only when it's safe and reasonable to do so. Also, "swung into the traffic lane" brings to mind a cyclist swerving into traffic unpredictably. It's important to always look back to make sure you have the right of way and won't be swerving into anyone's path before "swinging" over, and to negotiate for right of way when necessary.
No one honked. No one yelled. No one stomped the gas pedal and made a big fuss about resuming their speed. They all got it. I thought so they didn't have to.
But yes, many drivers are often confused and nervous about overtaking cyclists, and direction from the cyclist, offered clearly and assertively, including by taking the lane, is often helpful and appreciated.