The main concept he is trying to get across is that for an overseed on an existing lawn it is not necessary to "rough up" or loosen the ground. If you have thatch blocking the way, then dethatch. If not, just scalp the area and overseed.

Here's what a really knowledgable person has to say ( Although he is talking about a renovation, Once you have thatched or otherwise revealed bare soil, You should follow his advice that follows after the three "***..." that I added:

Posted by tiemco 6ct (My Page) on Mon, Aug 20, 12 at 21:56

Well I seem to do a write up every year regarding this, so here goes. When you kill everything and start fresh it's called a renovation. To do it correctly, one usually starts with a soil test in the spring to give you enough time to add amendments to bring your deficient macro and micro nutrients up to a good level. You said you are adding lime. Is this due to a low pH, or is it just something you generally do? Are you using calcitic or dolomitic? Anyway, lime should be added either way before or way after seeding, say a month at the least. It will take a while for lime to dissolve, and if you apply it at seeding you can get interactions with starter fertilizer and the very top layer of soil can have a much higher pH than you want. So if you are going to lime, either do it now, or wait till a month or two after you seed. For Round-Up to work its best, the grass and weeds need to be actively growing. Watering a few times a week prior to applying Round-up and after applying will make it more effective. Once you notice the grass starting to die, usually in 4-7 days, you will want to mow it as low as you can before it lays down. Once it's down, it's a lot harder to mow. Many people allow a period of fallowing at this point, applying water to get any dormant grass to reanimate, and any rogue weed seeds to germinate. If you aren't going to fallow, that's fine, it's optional. So now you have a brown lawn, and the soil should be fairly moist from the waterings. The next step that I like to do is power rake, especially if you have thatch, or the soil is obscurred by dead grass. TTTF seeds are pretty big, and they can have trouble getting to the soil if thatch is an issue or you have a lot of dead grass matted down. You can skip this step if you want, it's optional, but I like to do it. It also loosens up the top inch or so of soil. *************** After a power raking, either rake up all the loose dead stuff, or use your mower with the bag to remove it. Now you are ready to seed. I like to do all the prep work the day before, and the seeding the next day early. A light watering the night before seeding is also a good idea. So now you're ready to seed. Use a broadcast or drop spreader, whatever you feel more comfortable with. Apply the correct amount of seed, more is not better. If it says 8-10 lbs per 1000 square feet, shoot for 9. Make multiple passes in different directions to make sure you have even coverage. If you do this, be sure you lower the setting on the seeder so you don't put down too much on the first pass. Once all the seed is down you have a few options. One is do nothing. Some people like to roll the seed with a water filled roller. Some people like to top dress the seed. Some people like to do both. If I could only do one, I would topdress. Another thing some people do is apply Tenacity herbicide at the time of seeding. If you have a lot of weeds, or anticipate a lot of weeds it can really help reduce them at seeding. Now that the seed is down, and you rolled the seed and or topdressed, an application of starter fertilizer is a good idea. I like to use a half app at this time, the other half after the first mowing. You can use a full app if you want, but with all the watering you do I feel that you lose a lot of that full app due to leaching. Now it's time to water. Watering is probably the single biggest factor in success. The seeds need to be moist continually until they have all germinated. This generally means three light waterings per day. If you have a sprinkler system, then you are golden. If not, you need to set up hoses with timers. You can do this when you water prior to rounding up. Make sure the whole lawn gets adequate coverage. You are watering to keep the seed moist, so no puddling. Generally this means 5-15 minute watering cycles depending on your water pressure and coverage. Three times a day is generally enough. Then all you have to do is worry about your seeds, and the weather, and everything else that can go wrong. Once all the seed is up, and you see the green fuzz, you can start to cut back on the waterings to twice a day for about a week, then once a day for a week, then every other day, etc. Your first mowing should take place about a month after seeding, or when the new grass is 3 inches tall. Mow it down to 2. I'm sure I forgot some things, so please ask questions, and this isn't the only way to go, but it has worked for me very well.