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The best way,IME,is cut the knot flush to the handle,use a 1/4 inch drill to make a series of holes around the middle of the knot.than get in there with plyers to pull the hairs out,works every time.

Boar knots

Is your intent to buy the omegas, remove the knots and re use them?? if so that is nearly impossible..
Boar knots are cheap,cheaper than the cheapest Omega brush.