>>7651977 (OP)pick a large brush
the largest you can to depict whatever block of light or color or organizational structure you want to depict
need more details? pick a smaller brush
the largest you can to etc.
does the next smaller thing you can depict inside that block not matter? do you not want to draw attention to it? do you want to draw attention to the subject instead? leave it as it is (that's your messy background)
go to youtube and watch oil painters work in real time, anon
it's not rocket surgery
you'll get there