I know this is about paint, but I have had great luck with cutting Elmers glue 50/50 with water and gluing backgrounds on. It increases the brightness of the background at least 2x.
Just to be the odd man out, I'll say that I painted my 150 with this:
I used a foam brush and had to apply a few coats. But the ends justified the means--very durable which was the objective. And I don't expect to ever change the color unless I remove the entire back pane of glass! And it is very noxious, paint outside.