Painting a set of wooden shelving is a task that's certainly simple enough in concept, but getting a good paint job can be an elusive goal. Applying paint to flat, sideways and upside-surfaces in the same structure creates one set of challenges while the texture of the wood requires special considerations. Prep the wood and plan the paint application to get a smooth finished product.
Assemble the shelves before painting. The paint will add thickness to the shelves and alter their texture, making them a little stickier. This may interfere with your ability to put them back together if you paint the pieces while disassembled.
Strip away old paint, if desired, using gel paint stripper. Follow instructions on the stripper's container.
Sand the wood with a disc sander. If you haven't stripped down old paint, sand any chipped areas of paint to make the edges of the paint smooth. This will prevent the edges of the old paint showing through the layer of new paint. Smooth the front corners of the wood and spend a little extra time sanding any areas that are rough or seem to be starting to chip or splinter.
Apply a coat of primer paint to the entire set of shelves. Keep the application of paint as smooth and even as you can but don't worry too much if the texture's imperfect; the point is to create an evenly coloured palette for top coats of paint. Let it dry.
Paint the undersides of the shelves. Let these areas dry before you continue so you won't ruin the paint job by accidentally touching the undersides while you paint the other areas. If any paint drips onto the top of the shelf beneath, smooth it out while it's still wet or wipe away with a damp rag.
Do the back and sides of the shelves (if any) once the underside is dry. Paint from the bottom up to prevent too much pooling of paint at the bottom.
Paint the surface of the shelves where the items will sit.
Work paint into cracks and crevices in the shelving unit.
Paint the back, top and front of the shelving unit. Keep the paintbrush strokes parallel and work for the smoothest application of paint you can in these areas as they'll be the easiest to see.
Give the paint a second coat. Apply in the same order than you painted the parts of the shelving with the first coat.