A.Bill Feist, a former wood-finishes researcher with the Forest Products Laboratory in Madison, Wis., and co-author of Finishes for Exterior Wood, responds: That should work fine, as long as the substrate is properly nailed and in good condition and there are no obvious moisture problems.
Treat the old finish the way you would any coat of paint: Remove loose and peeling finish, then sand the surface, taking care to feather sharp edges left over from scraping. Any bare wood should be sanded, too. And if the old surface is shiny or glossy, sand it or treat it with a deglosser so the new paint will adhere.
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