For large a decoration in the home, a bed sheet makes a workable surface. To paint on a bed sheet, it is best to prime it with paint to make it less absorbent. In addition, the white primer will make the bed sheet like an artist's canvas. Some artists have even used latex paint to prime canvases. Although it is not an archival way to prepare a surface, for a home decorative use or as a hobby, the latex paint will function adequately. Once the surface is ready, you can create your design, pattern or other idea.
Tack the bed sheet on a large wall.
Apply two coats of white latex paint. Do the first one vertically and the second horizontally. This seals the fibres. Use the widest brush you have. The paint must dry between coats.
Sketch your pattern on the bed sheet, which is now primed, using the pencil. You can also use stencils or other graphic aids. In addition, if you have an opaque or other kind of projector, you can project a picture onto the bed sheet and outline it with the pencil.
Paint your design. You can use artist's acrylic paints, if you have them. Old latex house paint from prior jobs will work fine, too. Mix the colours in cups or cans, stir with a brush and apply. To avoid drips, start at the top. From there, work your way down. Of course, you can always paint over drips later on. Enjoy the process.