Another way, which I started with way back when, was to make a copy of the song (to preserve existing) and hard write fades using the Edit-Gain Change plugin.
You can try it, undo, try it again, add, undo again, etc.

You can also highlight a given section of multiple tracks and fade from 100% to 80% .. then highlight the rest of the ending and fade from the pre-mentioned 80 down to zero .. or any multiple combinations of fades, which can create a an implied curve.

Just another way to do it (old school) .. lots of options.

Many times I'd get the mix done, render to stereo wav then work on fades (even if still in RB with a wav file).

Those hard write edits mentioned above are un-doable until you reach your limit or save the file.. so you can undo and try various fades quickly.

Make your sound your own!
.. I do not work here, but the benefits are still awesome