You may be able to knock the gloss down some by using semi-gloss or matte polyurethane, which'll help add a little protection to it, but I don't know if it'll knock the sheen down to an acceptable level.
Whatever you do, take a piece of scrap you have left over, paint it the exact same way, and test whatever you're gonna do on that scrap to see if you're satisfied with the results, otherwise this could get expensive for you.