I found the Slick50 ( yes, it's still available) to be a great product with how it binds PTFE to friction surfaces. I haven't used it on the Guzzi but have seen good results with it in autos since first using it 25 years ago.
The current thinking in lubricants, if I may summarize:
In the bevel box: gear oil and moly, ( Guzzi has a mixed product " final drive oil"), or gearoil with no moly or synthetic ( or no).
In the gearbox: Redline Shockproof heavyweight ( or lightweight), or synthetic ( or no). No moly.
In the motor: fermented rhinoscerus semen ( how you get the semen out of the rhino is your business). No, really, I know it's true. I read it on the internet.