I've created a new cr3runner 2.6 installer for Kindle 4 NT (works for 2011 and 2012 models). This way installing CoolReader is much easier:
- copy everything from cr3-dist.zip to Kindle
- copy update_cr3runner_2.6_install-k4.bin from cr3runner.zip to Kindle
- install update from Kindle menu
Now open CR3 Runner v2.6 kindlet on Kindle and press middle joystick button to start CoolReader 3.