Painting on fabric provides so much versatility. The altered fabric can act not only as a background but also as a layer in your collage work. After the initial layer has dried, additional layers of shading and paint can be added as stampings and other imagery. Think of the painted fabric as not only a background but a potential element in the composition.
Prepare your work area with either a silicone mat or a piece of wax paper. Cut the fabric to size. Lay the fabric on the surface and apply paint in a thin layer with a wide brush.
Always start with a dry brush when applying paint to fabric, and if you need to rinse your brush, dry it as much as possible prior to adding more paint.