We recently painted this house with deteriorating LP siding. The white spots are elastomeric patching compound, which we always use to fix up exterior wood products (and stucco). The next picture isn't great, but this side of the house was completely wrecked. We scraped the undersides of every board, primed all of it, sealed it with elastomeric, then painted it. It's labor intensive, but it works well. I really need to start taking the time to get good before and after shots, but we're so busy I'm always trying to get work done and forget. I'll post some better shots of this house soon so you can see how good it looks.