You'll want to avoid I-75 completely, from West Chester all the way down to Florence Kentucky. Avoid I-71 between Fields-Ertel Road and the Norwood Lateral (SR 562). Avoid I-275 between I-75 on the north side, all the way east and south around the city to SR 125 (Beechmont Avenue).
Those are the major headaches. Cincinnati has various other thoroughfares that obviously get more traffic during rush hour, but they are too numerous to list all of them. Main ones I would avoid would be Colerain Avenue (US 27), Cross County Highway, Norwood Lateral (SR 562), Montgomery Road, Mason-Montgomery Road, SR 32 between Newtown and Batavia, Beechmont Avenue from Five Mile Road all the way out to Amelia in Clermont County, Tylersville Road in West Chester, Dixie Highway in Fairfield, I-471 south from downtown to Highland Heights and on down to Alexandria (no longer an interstate past Highland Heights, but still busy), and I-275 from the airport over to I-471.