We maintained 3 miles of gravel road (well traveled) for 12 years using a simple drag very similar to the yellow one AIRBISCUIT shows.
The main difference was that ours had only 3 blades angled about the same as his pix shows.
We pulled with 2 chains left corner to left bumper rt to rt.
Note carefully that the mid blade is wider than the front in order to catch spillover and the mid blade spills over to the back blade.
This configuration slices off the bumps, fills the voids etc.
The 3 blade design avoids creating dips and bumps.
We generally graded twice a year.
Later we added a small deck that a rider would stand on hanging onto a rope.
The rider would stand spread eagle fashion and apply more weight either left or right side and effectively steer the grader as he pleased.
Couple of years ago I welded up a 6ft X 6ft 'grader' using scrap 3" X 3" angle stock for a buddy which he uses to maintain the passageways at his public storage facility, this he pulls around with his
B21 Kubota.
About the only improvement I can think of would be to add teeth on the front cutting blade to increase the loose material as his drives get well packed down as he has lots of 'fines' that pack tightly.
I did weld scrap expanded metal cage to add weights for better cutting action.
This type of 'finish grader' could be fabricated very expensively however shipping would be a major issue.
Maybe a 'DIY' kit 'ready to weld' could be an option. Bolt up version could also be an option.
For an ultimate finish, simply drag an 8ft X 8ft section of chain link fencing.