Questions on mowing and weed killing after overseeding
I am a first time home owner and I just moved in end of May. The previous owners had a dog so the back lawn (which is pretty small - it's a half duplex) was full of dog spots - about 50%. It was also full of dandelions. It has a detached garage in the back and on the one side of the garage, the grass was pretty much dead and full of yellow straw like hay. The front lawn wasn't bad, but was a bit thin and had a few dog spots as well. So, I decided to overseed.
I didn't really know anything about lawns or grass before all this but I did quite a bit of reading and have learned quite a bit. I don't know what the existing grass was but if I had to guess, it's probably fine fescue. I mowed the grass as short as I could with my Yardworks 14 inch reel mower. I dethatched for hours with a dethatching rake. I pulled dandelions (as many as I could). I core aerated with a manual aerator I got from Home Depot. I put lime on the dog spots. I top dressed with Scotts enriched lawn soil (about 12 bags of it overall) covering about 1/4 inch of the topsoil. I spread Scotts Premium Sun and Shade mix with the Scotts hand spreader and finished off with Scotts starter fertilizer. I then ran my leaf rake upside down over the lawn to press the seeds into the soil. Finally, I watered the lawn.
I did all this about a week ago and have been faithfully watering twice daily to keep the soil moist. Now, the existing grass is pretty long (about 4-6 inches) and I think the seed is just starting to germinate. It's hard to tell because of the existing grass but the mix is PRG, Red Fescue (I think) and KBG. I think it's the PRG that's starting to sprout. Also, the dandelions are starting to grow tall and my front lawn is starting to have quite the population (I think partly due to my neighbor who neglects her lawn and has a million dandelions growing).
So, my first question is, when do I mow? I've googled and googled and googled and I'm getting different views. Some say wait as long as possible so as not to disturb the seedlings. Certain pro articles say keep mowing and keep it at 1.5 - 2 inches so the seedling are not in the shade of the tall existing grass. Some say, mow when the height of new grass is 2-3 inches. Now, if PRG germinates at 7-10 days, red fescue at 14-21 and KBG at 21-28...when the heck do I mow?? My other concern is that the existing grass is getting long and it might be depriving the seedlings of sunshine. But if I mow using my reel mower, I will be leaving long clippings which can smother the seedlings. If I rake them, I might be uprooting seedlings. If I borrow my dad's gas mower so I can bag the clippings - other articles/forum discussions say that it will suck up the seedlings. I'm so confused.
Also, regarding the dandelions..(I think all the weeds are dandelions, I don't think I saw crabgrass and I don't know what quack grass is or other weeds). Can I spot spray with Killex right now? Or do I have to wait until the new grass is established. Better yet, can I broadcast spray the Killex? If so, when can I do this? Killex supposedly doesn't affect the lawn but the label doesn't specify regarding new seedlings. Some articles vaguely say to wait 8-10 mowings before doing any weed control but I don't know if that applies to Killex per se.
It's day 8 since I overseeded and I am constantly thinking whether I should mow the lawn now or wait. If I wait, I'm wondering when I should do it.
Please help and thanks in advance.