Fiberglass to Steel

Im having some problems with a car we're working on in our shop. We are molding a fiberglass spoiler to a steel trunk lid. The 1st time around we just used dynaglass to adhere it and smooth it in, left 1/16inch+ over the seam, and after paint, the seam showed right up. The second time around, we put glass cloth and resin down, bodyfiller, primer, then paint. After paint, the texture of the fiberglass cloth, and the panel edge, show through the paint. Never really do fiberglass work, so i have no clue on this. Anybody have any ideas to Help me?