Epoxy is the perfect material to make permanent repairs of rotting window sills, door jambs and exterior molding that are difficult to remove and expensive to replace. Epoxy is easy to handle too. You mix it like cookie dough, mold it like modeling clay and, when it hardens, you carve and sand it just like wood. It sticks like crazy and is formulated to flex and move with the wood, so it won't crack and fall out like some wood fillers.
You've picked your color, but how many gallons will you need for your room? Calculate the wall area of the room; you'll need one gallon for 450 square feet. To determine the wall area, multiply the height of each wall by its width (don't subtract for doors and windows unless they take up more than half the wall); total the figures for the walls. Add 10 percent for future touch-ups. For two coats, double the number.