The best way that I can see is to try to get the knot out of the handle completely. That way you can re-epoxy it back in. You really won't be able to get any epoxy into the handle with the knot still in.
I repaired a Semogue after the knot fell out once and I noticed that the knot fit the metal cup in the handle very tightly. I suggest you keep trying the work the knot out of the handle. Try turning it as you pull and see if you can coax it out.
Failing that I have a radical suggestion. Follow this at your own risk. I repair guitars and in my business sometimes I have to repair cracked instruments where the crack is so fine that it can't be opened enough to properly apply hide glue or Titebond to glue the crack shut. In such instances I use water thin super glue. It wicks down into the finest crevices and cures very rapidly and makes for an excellent repair. You could try that. You'll want to use a pippette to apply the super glue exactly where you want it and to control exactly how much glue you're applying. I've never done this to a brush but my theory is that the glue will wick its way down under the hair knot and repair the failed epoxy. If you can't get the knot out it's worth a shot.
EDIT: I can foresee the possibility of the super glue wicking into the hair knot itself ruining the brush. I believe Semogue seals the base of the knot with a resin which might prevent the glue from being absorbed by the hair knot. However, don't proceed with the superglue option with out due consideration of the consequences. Were I in your position I'd probably try this, but I've had experience using super glue in this way. You may want to shy away from it if you're worried the brush might be ruined.
You should be able to find a water thin super glue at a woodworking store. I don't know if you have a Rockler store down-under, or someplace similar. If not, and if your hardware store doesn't carry water thin super glue you can put regular super glue in the freezer. When super glue gets to freezer temperature it gets more runny rather than actually freezing.
Let us know how your repair efforts go.
Last edited by Foyle; 08-09-2012 at 06:29 AM.
TOFLAC-U, AOM, LEMS/ Stay back! I have a Merkur, and I know how to use it!