If I paint a project it is usually with a airbrush, the backer is usually done with flat black rattle can after using painters tape around the edges & any other places that wont be seen ,it gives the glue more sticking power on the bare wood. I apply the glue with a 2 inch foam roller to the back of the project & use plenty of clamps while drying ,then a couple of coats of spray satin varnish