I too remember when I learned that passage that it was the most difficult part of the work. Practicing at slow tempo is definitely a good idea, although it has made it somewhat difficult for me when the tempo was really very slow.
What I did was to learn each part separately, then practice right hand and pedals. If found that (being right-handed myself) the pedals and right hand was the "support" for this complex passage. Once you can play that in performance tempo, then you can take the tempo down a notch and practice only left hand and pedals. By that time you will be well familiar with the pedal part and you can concentrate more on the left hand. Once you can get the left hand and pedals up to performance tempo, you have basically won the challenge. Add the right hand to the mix at slightly lower tempo and you will quickly get everything right.
The key thing for me here was to properly learn the "support" (right hand and pedals) and gradually adding the left hand. Also, at very slow tempo it really became a bit difficult for me to play the left hand and pedals due to the "over-focusing" on the rhythm. If your "support" is steady enough, you can easily add the triplets in the left hand without too much trouble.
Good luck in learning this amazing work! Once you get through it, it is one of the most enjoyable pieces to play! Enjoy!