A.Robert Sanders, a restoration contractor in Pasadena, Calif., responds: Prepainting might seem like a good idea at first, but you’ll get a better job in the same or less time if you paint the crown in place. The fact is, the walls and ceiling always have some irregularities and the crown may be warped or cupped. Inevitably there will be gaps where the crown meets the walls and ceiling, and for a professional-looking job, these gaps must be caulked. The caulking, plus any spackling at nail holes and joints, must be painted. You might try cutting in just the caulk lines and touching up the spackling, but since neither latex nor alkyd enamel patches well, the areas you painted in place would likely show up.

I would prime and sand the crown, then install it. Spackle, then sand smooth all nail holes, corners, and joints. Spot-prime all spackling. Fill any gaps behind or above the crown that are larger than 1/16 inch. Caulk the entire length of the crown, at both ceiling and walls. Top coat with two coats of enamel, then cut into the crown with the...

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