RE: Painting a boat
You should have kept the gelcoat on there. That layer is there for a reason, to keep the surface free of slight voids and pinholes. Gelcoat is also the best primer for your paint as anything will adhere to it. You will now need to use a high build primer, scuff once dry, or wetsand. A few coats may be in order depending how "rough" the glass is before you begin applying your color whether it be a one step, or a basecoat/clearcoat.