Having played this piece (and never really mastered it to the level I wish I could), I can say that it totally lives up to its nasty reputation, and before going further I want you to examine whether or not you are actually ready for it. If not, wait and come back to it in a year. If you think you can do it, then get ready to dig in. There's a LOT of work involved in polishing this piece.
The most important way to work on something like this is section by section, phrase by phrase, measure by measure, even note by note. Repeat the fast sections as many times as you need to be able to play them perfectly three, four, five or more times in a row. Practice mindfully, watching accuracy, dynamics, shape, and touch. Vary up your work--practice a legato section staccato, block the harmonies into chords and practice it that way, play it in swing rhythm. When you're working section by section, work backwards by starting at the ends of the phrases and adding the preceding notes one at a time--slowly, not adding until you've mastered the notes after it.
Also, throughout, practice and memorize the hands alone, then add them slowly. In addition, especially in the coda, try playing the right-hand part with your left hand, and visa versa; try ghosting (playing one hand normally, the other lightly or even silently) each part; even try playing it backwards.
In the fast section at the beginning of the piu animato (specifically the run in mm. 111-118), look very carefully at the fingering in your edition, and then FOLLOW THAT FINGERING. I made this mistake repeatedly, and it sabotaged my accuracy for months before I figured it out. To be honest, when I started this piece, I had no real idea how to attain the kind of clarity that is necessary for this piece, but over the course of about two years I basically "invented the wheel" with this (and I'm still working on applying all of these in my own work). Practicing effectively will save you SO MUCH time, and MONTHS of frustration. These principles are not only helpful in the Ballade, but in all your repertoire--and it will shrink the amount of time you spend on the notes from months to weeks, or even days.
These are all just my opinions and nothing more.