There are several ways to quickly break in a disc but none can replace breaking them in over time.
Some options:
- Thumbers, thumbers, and more thumbers
- Rollers on concrete
- Throws into walls/the ground
- Wrap it in a towel (optional) and throw it in the dryer on no heat with occasional tests to see how it is
- Skip shots off pavement
- Multiple one disc rounds with it on a heavily wooded course
The other thing to do is to familiarize yourself with the concept of the Parting Line Height, or PLH as you'll find it here. The higher the parting line, the more overstable the disc. Take the disc that's seasoned the way you like it into the store with you and compare it with the available discs in the mold you want. Look for a replacement with a lower PLH, and it will act less overstable/more understable than the one you like did when it was new. Just know that, as it seasons, it will season to be less overstable/more understable than the one you like is.
One last option I'll give it to start seasoning a fresh disc now. Once it gets to the flight you like, put it aside and start on another new one. That way you'll always have a backup.