Typically a cow/heifer is our of standing heat by the time she's AIed. Even if she is still in and just going out, if you wait 24 hours she won't be bred by the cleanup bull till the next heat cycle. A vet can tell by palpation that 3 weeks difference. If he/she/it can't, time for a new vet. Plus she will generally calve later to the cleanup bull. But, there are alwasy the cows that are w eeks late or two weeks early.
A friend of mine used to use an Angus bull then a Hereford for cleanup. Not much chance of getting that wrong.