For your client's lawn renovation, aim to aerate and overseed with Fescue in early to mid-fall, around September or October, to ensure good establishment before winter. If you need quick coverage, consider adding perennial ryegrass a few weeks before the Fescue. Apply pre-emergent herbicide in early spring, as applying it too close to overseeding can prevent seed germination. Continue monitoring for weeds and use
post-emergent treatments once the new grass is established.