I would stay away from Wd-40 on antlers, over time it will collect more dust than u want !there are products out there made for taxidermy that your taxidermist should be able to help you! I have a couple bottles I keep on stock to sell
Is it a quality antler mount or just a cheap plaque kit from walmart? I used to use the cheapos. Several years ago I learned to use taxidermist blocks to mount them and make my own plaques. The difference is night and day. Takes a little while to make a nice mount, but im slowly going back and remounting my old ones with the new method and quality plaques.
If these are in your house the dullness is from things in the house,like cooking. Wipe them off with alchol and then try some stain like minwax. Walnut was my preference. And buff them with a cloth. they will polish up but not like glass just a little luster will come on them.