My method (which will make more sense after you read that thread):
1- cut down bristles as low as possible
2- tape up handle to cover anything you don't want to scratch which for me is the entire thing...and I mean I put 3 or 4 layers of tape because you will slip
3- use needle nose pliers to pull out as much hair as possible - you also could get lucky and have the old one just come out
4- use forstner bit to drill out rest of knot, stopping every so often to go to town on it with the needle nose pliers again...a lot of time large chunks will just pull out once the integrity of the glue is broken - go deeper than you need to - once the knot is basically gone but there are a few straggler hairs left I take out the dremel with a sanding bit and just give them a once over...and get rid of any remaining debree - there are several dremel bits mentioned in above link that work great for other hardships you will encounter
5- Measure the width of the hole to figure what knot you will need or what you can do to the hole to make it wider if you wish
6- Purchase highest quality knot from Blankity-Blanks of the proper width
7- Receive knot and determine how deep you wish to set it (I prefer pretty deep)
8- Measure the depth you wish to set it and then one of two options A) fill it with marine epoxy up to the level (letting it dry for a day afterwards) or B) epoxy in a slice of wine cork to that level
9- Once the new shelf is set you can polish the outside - I use anything from nail files, to sand paper to polishing clothes/dremel cloths combined with flitz and rubbing compound
10- Dab a small amount clear marine epoxy on the shelf, dab a small amount of clear marine epoxy on the base of the knot, securely place the knot into the handle.
11- Let sit for 24-36 hours
12- take a picture and post it in the share your restorations thread
Might I also suggest practicing on a cheap thing you get off ebay prior to attempting one you care about, such as one from grandpa - I screwed my first one up big time.
Each step in my method is analyzed and re-analyzed in the threat above - but this works for me, I've restored 8 or 9 so far.
I am willing to do it for you. You can see my work that I did on two previous brushes, soon to be three. Let me know what you choose. We can work out a deal if you would like to.