Clean it off with a wire brush and dry it for a while (3-6 months).
Cut it a bit oversize.
Potassium Permanganate ( pool supplies store) can be brushed on the sides to make it darker. It looks bad at first, but after clean-up and some sanding and buffing it is the look most folks expect when they see stag at a show.
Don't paint the crown socket, as it is almost always left white.
Buff lightly with pink or white compound an a linen buff. After the initial buffing, you can lean in a bit harder to darken the high points.
Try all this on some scrap from the shed first, as results vary.