What kind of epoxy

[byscott]

I think more important then the brand or set time of the epoxy is properly prepping the socket and the knot plug.
I seal the inside of the socket at the beginning of the finishing process with the same finish used on the outside of the handle.
I rough up the knot plug with either 80 or 120 grit sandpaper so gloss is removed form the plug and it has a good surface for the epoxy to bond to.
I apply epoxy to both the socket and the plug and when I insert the knot I twist it slightly to make sure I have complete contact with no voids.
I keep a bottle of 91% alcohol handy to clean up any squeeze out.
I also mask off the hair at the line where it meet the handle to prevent any epoxy getting on the hair.
A bad job setting the knot can ruin the looks of an otherwise nice brush.

+1 on the advice about clean, roughened surfaces. I haven't epoxied that many shaving brush knots, but I have glued up about a mile of golf clubs over the years -- and as far as I know, they all stayed that way ;-) The key to a good solid bond is careful prep of both surfaces.