We maintained a 3 mile much travelled gravel road for over a decade using a drag about 2-3 times a year.
It was quite simple.
About 8 ft X 8 ft with but 3 blades.
Front and rear both angled slightly to the left and center to the right with an angle about 2X the other 2 Angles.
Front chops highs , next angled blade moves loose material sideways and fills the voids while the rear blade finishes the job.
Usually 2 passes left a very nice roadbed that lasted a few months of modest traffic.
This basic concept was what the highway department used in rural Quebec back in the 40/50's even using a team of horses early on B4 they adopted trucks.
3 blades was the trick as they kind of established a reference base. Less blades would tend to add to the ups/downs much like the frustration of using a simple back blade on your tractor.
LOL, our drag was bolted wood frame with 3/8 X 3 inch flat stock simply lag bolted to the faces as cutting edges. 2 chains attached to an old Willis jeep provided the power.
Couple of guys, 2 hours and a few cool beverages completed the ritual.
We later on got even fancier as we added a slight platform and hand rope so that a volunteer could ride the drag and steer it by shifting his weight from side to side (not OSIA approved, but it worked) much like riding a surf or wake board.
Now if U wish a super fine finish simply drag a section of chain link fencing.