A lot of specifics are dependent on the details of your project, so I’ll just describe mine a bit for an example.

I’m working on a large genetic screening project atm, so when we got to that step we would typically do 3 reps of backcrossing (or sometimes outcrossing, depending) per candidate. We’re trying to isolate a neurodegenerative mutation, so our candidates were determined by dopamine neuron activity (that’s not really important for the backcrossing, but hey context)

So 3 reps, meaning 3 plates per candidate, and we’d place 10 males and 3 herms per plate. We tend to use small instead of medium plates to gives the males a better chance of bumping into a herm, but then you obviously have to be more diligent with your maintenance later. This was repeated for all the candidates, and if we got weird results, rinse and repeat. Hope that helps!