Clean the Hardware
Examine existing hardware to discover what they are made of or whether they have been previously painted. Older wood hardware that has been painted several times will need to be stripped of its paint before proceeding. In many cases it may be less expensive and certainly less time consuming to simply toss the older wood knobs and pulls and replace them with new ones---wood pulls and knobs are priced for budget conscious do-it-yourself projects. Search for replacements at home improvement or hardware stores.
Clean Metal Hardware
Older metal knobs and pulls covered in paint can be cleaned up by using a crockpot, water and a mild detergent. Place the items in the crock pot, cover them with water and add 2 tablespoons of liquid laundry detergent. Cover and set the crockpot to a medium heat. Allow the contents to "cook" for 10 to 12 hours, then turn off the heat and remove the contents using tongs. Do not leave the crockpot unattended. Use caution when removing the hardware, it will be very hot. Place the hardware on disposable work towels. The paint should fall off the metal with a gentle scrape---use a toothbrush on intricate detailing.
Clean Glass Hardware
Glass knobs should be cleaned with rubbing alcohol to remove dirt and grime. Heated vinegar can be used to remove paint from glass. Heat a cup of vinegar on the stovetop. Once the vinegar boils, remove it from the heat and turn off the stove. Carefully dip a clean cloth into the vinegar and wipe down the glass hardware to remove the old paint. Rinse the pulls and knobs before painting.
Prep for Painting
Sand rough spots off of wood knobs and pulls. Wipe the knob or pull clean and then apply a wood sealer to prevent the paint from soaking into the wood. Prime metal knobs and pulls with a spray primer designed specifically for metal. Glass knobs and pulls will not need to be primed. However, use enamel paint for glass knobs and pulls for the best result. Set up a well-ventilated workplace, away from flames or gas, when using any paint and especially spray-on paint and primer. Protect the surrounding area from over-spraying by covering work surfaces with plastic or paper.
Paint Knobs and Pulls
Knobs and pulls can be painted in three ways---completely in a solid color, partially by applying only a decorative design, or in a combination of a solid color that is then painted with a decorative pattern. Spray paint is a fast and effective way to paint pulls and knobs a solid color. Use several coats of the spray paint, allowing each to dry first before applying the next. For complete color coverage, turn the hardware or walk completely around it while spraying. When creating decorative motifs on the knobs and pulls, use enamel craft paints (found in art and craft stores). Complete each knob and pull by applying several coats of a clear spray lacquer after the painted design has dried.