How to eject a USB removable disk/volume, similar to the "Eject" function in Windows Explorer?

Eventually, I found out where I was making a mistake with approach #2.

It turns out that for some reason I was not setting the desired access correctly when opening the handle to the volume using CreateFile.

The correct access mode is GENERIC_READ | GENERIC_WRITE and I was passing 0. After correcting my error I was able to successfully eject the device using DeviceIoControl - IOCTL_STORAGE_EJECT_MEDIA, as well as with method #1, using CM_Request_Device_Eject.

Finally, it turns out that method #2 is indeed the method used by the shell context menu's "Eject" function. Using this method the device reacts correctly.