My glaze dried too dull

[Susan Kuban]

I used a brown "glaze" to darken the busy background of a portrait. The glaze consisted of several colors of paint that added up to brown, plus mineral spirits and the medium I use, which is called Max Horbund's #3 medium (it is the consistency of vaseline and comes in a tube). I don't really know what proportions I used.

This glaze did a good job of knocking back the brightness of my background, but when I completed the foreground, the background now looks very dull in comparison. Also, my brown colored glaze has made all those background elements a bit too similar in appearance.

Is there a way of removing the glaze safely? Or can I apply something that would heighten the color and make it come closer in sheen to the foreground?

By the way, I can't afford to wait six months to apply the final varnish - it's a commission that is promised for a particular event that will take place in two months' time.

Thanks, Susan