I lease timber land for hunting so I encounter these huge ruts frequently.
Note: working on ruts left by heavy machinery is a rollover hazard. Pay attention and be sure your ROPS is securely up and seatbelt is in good condition and on!
I am a novice at dirt work, however, this is my process using the attachments I have.
1. Pull disc harrow over the area to loosen the material. (Ruts are a combination of compacted soil as much as displaced soil)
2. Perform 1st smoothing with box blade and back dragging bucket.
3. Wait for rain to compact the area, or drive over many times with tractor to compact.
4. Use box blade to move material from any high spots to any low spots.
5. Final smoothing .
6. Allow natural vegetation to grow in.