Not sure what overseeder means for sure, but to me it means using a lawn spreader to spread grass seed. I'm guessing what elitetc has in mind: apply grass seed beforehand, and then aerate multiple times to work it in. Then maybe drag afterwards. (this is what we do most of the time).
Some guys aerate 1st and then spread seed (but we like it the other way around). Seed/soil contact seems to be crucial IMO (preferably with some sort of soil covering most of the seed). We double slit seed some lawns, but must me dry loam soil IMO.
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