There are a couple ways to remove the hand guard.
First is to loosen the clamp screws, this usually allows the hand guard to expand and it pops free of the loctite.
Then just slide the hand guard off the barrel nut.
Second is to try part one, if it doesn't work remove both of the clamp screws from the hand guard.
Then find a putty knife or thin metal blade to slide in the clamp on the hand guard.
(Warning this blade will have a mark on it after its been used so don't use your knife)
Then start one of the clamp screws into the threaded area (back part) of the clamp.
As you tighten the screw up it will push on the putty knife blade and spread the clamp open allowing the hand guard to be slid off.
Don't over tighten the screw as you could spread the hand guard too far, only tighten until the hand guard is free.
Once the hand guard is off the inside of the hand guard and the outside of the barrel nut can be cleaned with brakleen/MEK and a stiff bristle brush.
This will remove any residue and allow for the parts to be reinstalled again with new loctite.
If you have any questions feel free to email me and I can help.
Thank You
Andy
MI