You can overseed after adding the compost, but then you’ll need to cover the seeds with something else to protect them. You can use straw or a light layer of finely screened mushroom soil. I say put the compost on top of the seeds to reduce the work.

Not if you use compost that has been composted properly (165 degrees F for a minimum of 2 weeks and regularly turned). Most weed seeds are killed if compost is made correctly.

If you apply the compost when rain is in the forecast, there’s really no need to water the lawn. The compost can just sit on top until rain arrives.

You can use our Mulch Calculator to determine how much compost you’ll need. You can access it here: https://farm-kits.com/mulch-calculator/