I use Green Drop. It costs me $200 per season, and they come out 5 times for that price. My lawn looks great - no weeds.
I've always power raked my lawn. If you have a healthy lawn, you will not ruin it by power raking. Also, I have no weeds in my lawn, so power raking doesn't promote weed growth. I Aerate my lawn about every second year. i don't think it is necessary to do it every year, but I don't think it hurts it to aerate every year.
Don't over water your lawn - that promotes shallow roots. If you water it regularly - but not over water it, the roots will grow deeper and you will not expose them by power raking. Also, as someone mentioned above, don't set the blade too low - you only want to get rid of the matted stuff on top.
Everyone has a different method idea of how lawn is to be maintained. I find that what I do works very well. My neighbours hate me because my lawn is always nicer than thier lawn - at least I think that's why they hate me -

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