Give it 2 weeks. And in case where you have bare spots, I would recommend reseeding again in 2 weeks. Seeds need to be cool in order to germinate which is why summer is not a good time for seeding.

As for dandelions. There are several ways to handle them.

I have a tool that helps me remove the entire plant, roots and all because it will resprout even with the tiniest bit of root left.

I also use boiling water to kill the plant. I do this several times more in the following weeks in case the plant sprouts again.

Or last resort, is to use round up to kill off the weed.

I also minimize dandelions from starting out by debudding the plant so it doesn't get a chance to bloom and to form seeds.

Ianna

I have noticed that I haven't been able to remove the root all the time. Would pouring boiling water over the root be helpful or what about pouring vinegar over the root?

I would suggest to water the grounds well if you are trying to pry the plant out roots and all. It helps to loosen the soil and increases your chance to remove the plant whole.

If you are trying to use the HOT liguid method (water or water/vinegar method) - do not water the lawn beforehand (and thus strengthening the weed). Thoroughly drench the plant with the hot liquid. Later remove the dead portions of the plant and once again repeat the process.

Ianna