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A good pumpkin for painting has a smooth, even surface with no bruises, scratches, or blemishes. Pumpkins with light or very light or shallow ribbing will have the smoothest surfaces. Avoid pumpkins with too many lumps and bumps, or they will be difficult to paint. Look out for any cuts or wormholes that will cause problems, and make sure that the pumpkin is flat enough to sit upright.  Watch out for any soft spots in the pumpkin because that may be a sign of rot. You want your pumpkin to be fresh and to last as long as possible. Almost any variety of pumpkin can be painted, but the following are especially good: Baby Pam, Sugar Pie, Neon, Lumina, or Cotton Candy. Gently remove any dirt or grime using a dampened paper towel or a baby wipe. Use a soft, dry cloth to thoroughly but gently dry your pumpkin. Avoid brushing the pumpkin with a hard brush because you might bruise or scratch your pumpkin or just damage the skin. Take care not to get the stem area (top) or the blossom end (bottom) of the pumpkin wet. This can cause the pumpkin to rot. Before you start painting, you should have your heart set on a design. Almost any design can look good on a pumpkin, as long as it's not too complicated. Faces are popular, but you could also choose a black cat, bats, a haunted house, geometric shapes, or anything you like. Once you've chosen your design, lightly sketch it on a piece of paper for reference.  Let the shape of your pumpkin inspire your design. For example, a squarish pumpkin could become Frankenstein's head. Who says painting pumpkins is just for Halloween? You can paint your pumpkin to echo a fall theme, such as painting leaves or scarecrows, or just paint something completely random on your pumpkin. Have fun with painting your pumpkin and paint a self-portrait or a portrait of a member of your family. Though this is optional, applying a sealer to the pumpkin's surface before painting will help the paint better adhere to the surface. Purchase a craft-grade sealer at a hobby or craft store. Sealers are available in either aerosol cans or squeeze bottles, according to your preference.  Use a brush to apply a liberal coat of sealer evenly to the entire surface of the pumpkin, and allow to dry thoroughly. Clean this brush thoroughly if you plan on using it for painting. Give the sealer time to dry before you move on to paint the pumpkin.

Summary:
Choose your pumpkin. Clean and dry your pumpkin. Choose a design. Apply a sealer (optional).