Sure, greyosx. My method is more complex than fabioroberto's method but I used it because I'm familiar with the command line. This is all on El Capitan. I can't speak for Sierra, but I will likely do this on Sierra once that is released, so I'll try to update people on how that goes.
1. Disable system integrity protection
To do this, you need to enter recovery mode by holding down Command-R on boot up. Once in recovery mode, open the terminal and then type "csrutil disable". After that, reboot the machine.
2. Enter Console Mode.
Hold down Command-S on boot up.3. Backup the old kext.
First type "mount -uw /" to make the hard drive writable. Next, you need to make a temporary folder to store the backup. I used /_temp. Type "mkdir /_temp". Now we need to copy the kext to the backup folder. "mv /System/Library/Extensions/AppleGraphicsPowerManagement.kext /_temp/"4. Copy in new kext
This is where my method differs from fabioroberto's. I will use the command line to install the new kext. Fabioroberto used an app called Kext Drop. The exact commands to run here will depend on where your new kext is. Your new kext will be the one you downloaded from fabioroberto's post or maybe you made one yourself as per fabioroberto's instructions. My new kext was on my desktop. "cp -r /Users/greg/Desktop/AppleGraphicsPowerManagement.kext /System/Library/Extensions/"5. Install new kext
Run "kextcache -v 1 -m /System/Library/Caches/com.apple.kext.caches/Startup/Extensions.mkext /System/Library/Extensions/". I don't know exactly how this command works, but I got it off a different post about a similar problem. That post is here: http://www.asyncro.com/2014/03/24/macbook-pro-discreate-graphics-card-issue-fix-updated/6. Reboot
Type "reboot now". The computer will output some stuff to the command line and reboot after a minute or two. The first reboot WILL FAIL. That is expected. Don't panic. It should automatically reboot again, and on the second try it should boot normally.Good luck and let me know if anything is unclear.
Thanks so much for providing an alternate method, very interesting to see!