I made a collage, as you can see in the background of the photo, with pages from an old book covering the canvas and then another layer of pages loosely attached to allow the edges to look old and worn. However, in some spots on the pages covering the canvas, some small bubbles and wrinkles formed. I had painted the canvas with decoupage and then put another layer of decoupage over the pages. Would this be the correct method for a smooth finish? Is there a better way? What if I use different types of paper?