I like to sketch on gridded paper. It's a smooth paper that comes in pads from Quattro. All manner of pens move smoothly across it. Often I don't get what I had hoped in my quick sketch. But I do like to use just about everything. And sometimes after a couple days of resting I find that some abandoned sketches have a bit of charm I might have overlooked.
Well I also like to use up all my paint. I typically only put about a dime size dollop of paint on my palette. I use it up and add more. I never return paint to its bottle or jar. I don't want to contaminate the acrylic paint or ink left in the jar. (I use watercolors and gouache that rewet well so I just leave them on the palette and use them later.)
One day I noticed I had a bunch of rough sketches and a bunch of unused paint. I did some quick light washes over the sketches. Now I have bits I can cut up and collage into page spreads in the future.
I will try to post some of those as they come up.
Using rough sketches like these while I was creating collage samples for my on-going collage and sketching journaling class, helped me loosen up my own work.
Sometimes there are things we make (and draw) that really shouldn't be salvaged. But other times there are bits that we create that can be used in conjunction with something else to create a third thing that is neither of the first two, but something else entirely, and perhaps a bit appealing. We won't know unless we try.
The other thing that is fun to do with excess paint is paint paper and use that painted paper to tear up for collage material. See below.
Don't go out and spend money on decorative papers for collage—paint your own! Then you can tear them up and use them as little strips, or squares or whatever. The texture of your brush strokes adds to the variety and interest. If you use acrylic paint you'll be able to paint over these decorative papers, once they are in place, with wet media. How fun is that?!