We use Plugger brand aerators that plug deeper with more evenly spaced holes.
We clean all plugs from the concrete surfaces.
We recommend aerating your yard at least once a year. If your thatch is more than 1/4 inch. We would recommend 2 times a year. The best time to aerate is either in the Spring or Fall. You don't want to do it when it gets to hot or cold, doing so can cause damage to your grass.