When the primer is dry, caulk all small joints (less than ¼-inch-wide) in the siding and trim. Most pros use siliconized acrylics—paint won't stick to straight silicones—but Guertin and O'Neil like the new, more expensive urethane acrylics for their greater flexibility and longevity. O'Neil stresses that it's shortsighted to skimp on caulk. "If the joint fails, you're back to square one." Guertin uses the lifetime rating as his quality guide. "I don't expect 35-year caulk will last 35 years, but it should last longer than a 15-year caulk." Arvada Home Painting
If less than half the old paint is left, however, it may be worth stripping it all off. Guertin gets rid of stubborn remnants using shrouded grinders (like the PaintShaver), infrared paint strippers (such as the Speedheater), or chemical strippers (like Multi-Strip), then smooths the wood with a course or two of sanding. When siding (or bank accounts) can't take the shock of a total strip job, Rich O'Neil, of Masterwork Painting in Bedford, Massachusetts, has successfully hidden rough, well-adhered paint under Peel Bond, a thick primer.