[Darrell_KC]

Here's my own opinion from my experience. I understand you want to skip on the chemical component and that your objective would be to mow as short as possible and then seed. You COULD try it, but here's what I would think will happen. It takes time for the seedlings to begin to sprout. Once they sprout, it takes more time for them to grow and become self sufficient. During this growth window, you are throwing down a lot of water to keep things moist.

While you are doing your best to water and keep things moist, your scaled fescue will start to come back. As it comes back, it will grow faster than your seedlings will, and grow taller. That will cause the fescue to start shading out and stealing sunlight from the seedlings, and the fescue will eventually out compete most of your bermuda. Remember, during the first month, you cannot mow your lawn to keep the fescue short. You have to give time for the seedlings to root.

If you truly want to go the completely chemical free route, I'd say you have two options and neither are great and both bring their own issues and are extremely labor intensive. 1) Rent a sod cutter, and cut out the old fescue lawn. They aren't cheap, its hard work and very dirty and heavy and disposing of old sod sucks. 2) Rototill the old lawn. This will get you down to dirt, but will still stir up weeds/weed seeds, cause you to have an uneven lawn if you are worried about leveling, and again raking up piles of dead grass and dirt and disposal is a bear.

You are doing 6k square feet, my project was 14k square feet so you will have it easier than I did, but I went the normal route of glyphosate, scalp as low as possible, and then tried to rotorill the back, struggled mightily and resorted to using a SunJoe to dethatch/scarify and that helped immensely. I probably tossed out about 25 contractor sized bags of dead sod clumps and clay/rocks that came out from all the work.