My glaze dried too dull

[Michele Rushworth]

With the pigments and the driers/resins etc. in the medium I doubt there is anything that will remove just the most recent layer of your glaze. I would oil it out (I use a 50/50 mixture of linseed and mineral spirits) to bring back the sheen, and then repaint whatever needs boosting back up to its former level of brightness. You may need to oil out again when it's all done. I prefer that to retouch varnish, myself.