I am replacing both doors to my house. The front door/sidelite is wood-grain fiberglass (typical tan stain primed) and I have gel stain to do it. The back door is smooth fiberglass (mostly taken up by the glass in center). It automatically comes white primed for acrylic latex paint. Can I use the gel stain over this paint primer, or do I need to remove the paint primer and prime it with something else first?