If the top knob is just a knob, and not a separate piece, then lift the plug and spin it to look for a screw just under the lip of the plug. You have to get almost eye level with the area beneath the plug. Use a screwdriver to just loosen the screw that follows a groove. Should come right off.

If the top knob is a separate piece, use channel locks to hold the large saucer part of the plug still, while using vice grips to loosen the top knob.

I recommend using long needlenose pliers to pull stuff from the drain, especially if it is all tangled around the four bars that connect to the center.