cages around your trees will stop the bark eaters, as for paint i dont know ask you local nurserie they might have something.

First of all, where are you? I can't think of any place other than the mountains where there would be deer. As for the trees, if they have been girdled (bark removed all the way around the trunk), there is nothing you can do. If there is substantial bark left on the tree, put a cage around it (as suggested above) and leave it alone. The tree will heal itself.