If it has a nitro top coat, you might try rubbing a dab of auto wax onto a small spot to see if it helps. Several years ago, I aquired a fairly recent Gibson J-45 that had been sitting in its case for awhile and looked like someone had emptied a jug of milk on it. I looked around the web for some advice and came across a post from Bob Taylor of Taylor guitars. He said that nitro laquer was developed as a car finish, so auto wax can help restore luster on an instrument finished with nitro. I found some liquid Turtle Wax in my garage and tried a little bit in an inconspicuous spot. It worked great. I wound up rubbing out the whole guitar a little at a time and it came out looking like new. Wouldn't try it on anything other than nitro finish, though. Also don't know if it will cause problems with retouching finish dings or gluing up cracks in the future, but if it's good enough for Bob, it's good enough for me.