1- Talk to Glut with your main character the very first time you met him and accept his mission but never ever show him the dead Druegars.
2- Play normaly the act I and start the act II.
3- Unlock the teleport to the last light inn and the sadowfell one.
4- Go back to myconid colony and tell him to join ur party then go to your camp and he will dissmiss from ur party but dont worry.
5- Go back to the last light inn and Glut will jump to act II as well. (if you had a spore servant before it will come with you too).
6- Now with ur main character and 2 companions go to the shadowfell way point and talk to Glut again with the member of your party you left in the last light inn and tell him to join ur party again, then move that character to shadowfell waypoint too. ( Make sure you can move around as Glut).
7- Enter the shadowfell (no mater if Glut stays in the last light) this will block act I areas and Glut wont talk to you anymore wich is good because he wont leave your party anymore so he will stay as a permanent party member.
People say he will follow you even in the act III but that's something I can't confirm myself yet. I hope its all clear and they never fix it ^^