In regards the post of "perfect_pitch,": Sorry, but having to transpose the passage, sounds like it's over-complicated, and trying to do one passage in the original key and the other hand in C Major, seems rather pointless.
Plus - not all polyrhythm passages can be easily transposed into the diatonic key of C Major without the use of black notes. "
Okay, speaking for my own deficiencies, it has taken me forever to master the first three measures of the "Un poco meno mosso," section (two measures after number 15 of the first movement of the Rach 2nd). Nonetheless, utilizing the same C Major back and forth combination, it is now there.
If you have better mastery when it comes to poly-rhythms, my best to you. As an example, when I practice the Prokofiev 1st, (with its constant five against two), both methods work for me.