Depends on the lighting angles and natural light hitting the patch but generally add any chemical you might need to bond joint compound to paint, tape/mesh tape and feather it out depends on you're judgment mostly. Have you only ever done new construction and suddenly got a remodel job or something?
personally i 'slickcoat"(put on take off tight) all my patches on last coat. its mainly so i dont need to sand very much in a lived in home. you should be able to sand the edge into any smooth wall. prime and paint and it should good as new.
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