Hi. First post. Having driven a Mitsubishi I-MiEV for the last 5 years, I'm quite experienced at using neutral to coast. I've done it several times now with the Bolt.
Since there is no mechanical change between Drive, Neutral, and Reverse, it doesn't run the risk of damaging the gearbox to coast in Neutral. This differs from conventional automatic transmissions where they physically disengage the gears for Neutral; EVs are solid-state in this regard. However, the caution with the Bolt is that you don't accidentally press the Park button. That could be bad, as Park is a mechanical lock.
To engage Neutral while moving, you have to hold the shifter forward for about half a second, pressing the shifter button isn't necessary. You also don't have to press the button to go back into Drive or Low. It only needs pushed to enter Reverse or come out of Park.
As for coasting efficiently, you don't want to excessively gain speed and use air drag to limit your speed, you'll gain more by keeping speed down with regen. "Cutting it loose" at the bottom is fine, though. You'll also want to get in the habit of dropping back into Drive or Low to use regen when you need to slow down, preventing the use of friction brakes.
There are other situations where coasting is beneficial, not just on pure downhill runs. There is a road by my house where I can coast for a few miles due to the up and down terrain with a general descent. Coasting tends to push the trend bar up pretty quickly on this road. The longest I've kept the Bolt in Neutral was about 2 minutes, clicking into Drive and back to Neutral because of the uncertainty of the car going into Park automatically (I would hope a car from a major manufacturer wouldn't do this, but I'm not taking it for granted on a first year car).