In almost every case, you will need an extension ladder to reach a high gable. Use one that is long enough to reach the highest point of the fascia; using too short of a ladder and over-reaching is very dangerous. Make sure the ladder you use is in perfect working order, with the locking mechanisms intact and no bent rungs or side rails, warns the American Ladder Institute. Place the feet of the ladder approximately one quarter of the extended length away from the wall, on level ground. If the ground is sloping or uneven, purchase or rent ladder levelers. There are several styles--some attach to the ladder rails so you can adjust the feet to compensate for uneven ground, and others are a secure platform placed beneath the ladder.
Whether you're using a brush or an airless sprayer to paint the gable, an extension tool can help you reach past the point your ladder will reach. Purchase a brush extender, which allows you to clip the brush securely to the end of an extension pole. For spraying, use a spray tip extender. This is a lightweight metal tube that attaches to the spray gun. Screw the spray tip to the end of the extender to reach high areas.
If you can reach a gable on a split-level home by walking on the roof, plan on doing this in the morning when it's still cool. Most roofs get extremely hot in the midday sun. Use painter's canvas drop cloths or a strip of old carpet to protect the roof while you paint. Do not use plastic--it can be slippery underfoot. If you can access the roof through a window in the gable, save yourself the work of setting up a ladder to reach the roof and go out through the window.