Mr. Longbow,
There are two ideas here. First I have done both of these. You can rough up the fiberglass a littlewith sandpaper (to give the glue something to hang on to)and use titebond 2 or 3 and glue them down. After dry sand the edges and spray your chosen finish over them. you can also lightly sand the skins to end up with a smoother finish.
Or
If your not hung up on real skins there are several companies puting out limb skins. They are like Arrow wraps if you have used them. Basicaly a very realistic print of a skin. They are easier to put on as they are just 3M tape. They seem to hold up and can be removed.
I actually like that way better plus if you sell the bow you give the new owner the chance to remove them if you wish.
A couple pics.
First one done with real skins.
Next a bow with limb wraps from Arrow Wraps Unlimited
Before
After
