In my opinion the tiller seems like a great idea but... in reality... for a track that has this size of a turn out you should leave the tiller in the garden shed.
In my experience (I have prepped small tracks, big tracks, and just one turn at a time for practice) the tiller is great for the top 3 to 5 inches (nothing better as long as the dirt has the correct amount of moisture) and when there are not a lot of bikes about to displace the top 3 to 5 inches, but when it's dry, it leaves you with baby powder on top of hard pack. (perfect for a 4 wheeler) When there is not a lot of bikes, the tiller is a great idea, quick and easy.
Every track, track owner, and rider have their ideal prep method and out come in mind and in spirit. Every rider has their ideal prep for their perfect traction and every track owner will tell you those opinions vary drastically. The track owner that preps for the widest range of opinions will have the best success.
The saw dust is a good idea but don't discount sand if you have access to it. One can add just enough sand to allow the dirt to rip up easily, allow the moisture to penetrate deeply and not act like you are on a sand track. The sand actually creates space and surface area in the dirt for easier prep and longer moisture retention.
Have you seen what happens to the first turn at high point when it's hot, they don't water enough, and they run the tiller on it? Turns to baby powder like and no grooves for traction. Then they run the clump buster over the one berm that does form (creating more powder) so the next start doesn't need to deal with it entering the first turn. I applaud them for solving a dangerous situation on the start but I think it could be done better, say with a ripper and a smoothing bar. Then you would have lines develop the first lap.