The neck can bow forward or backward, so just saying 'bowing' isn't enough info. If the neck is bowing forward, tighten the truss rod. If bowing backward, loosen it.
I leave the string tension on and turn about 1/8 turn and recheck. Of course, the truss rod is just one of the adjustements than may be required - but IMO it's the first one.
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Taylor 810
Guild J30-12
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