My favorite way to eliminate the often paralyzing fear of "ruining" "good" paper is to just paint on any and all junk mail that comes into my house. Higher end catalogs are great for this, they don't use slick, thin paper (and even that gets used in collage or as a desk cover for other projects) and they're already bound for you. Just add marks! Carry it with you. Scan the pages you like. Cut it up later for making other art. It's "just" junk mail, so there is literally no pressure. I have HUNDREDS of these type of things and I run across them all the time, forgotten, in some old backpack or purse or drawer and it's a treasure to look through them again, and add new marks, paints and words.
A piece for an abandoned 5E adventure module; a portrait of the eccentric and reclusive host and owner (and victim) of the manor at which a garden party is interrupted by an unexpected murder.
