Scheduling - accomodating for overtime

What is the practice you use to accomodate for more "on the fly" capacity for the scheduling system?

Do you increase crew-size, hours per resource, a calendar(s), other?

Assuming the calendar is 5 days x 24 hrs. per day and sometimes saturday's and/or sundays are approved for specific work centers/resources. What is the method you are using to accomodate this random capacity increase?

Perhaps you let scheduling still run, but adjust on the floor by adding overtime and not changing anything in Vantage?