I've always struggled to play pieces where one part is in quavers (or any multiple thereof) and another is in triplets (or any odd number).
I'm going to have to finally conquer it, as I am attempting the Finale from Louis Vierne's Organ Symphony #1, which contains an example - albeit trivial - of triplets in the right & left hands vs. quavers in the feet, when the pedal theme returns (pages 50-51 in this score)
I can tap out the 'combined' rhythm, but using one hand (or foot, in my case) for only the quavers and the other exclusively for the triplets makes my brain switch to counting in either 2s or 3s, but never both! As a result the rhythm in one part gets squashed or extended to match my counting.
Any hints, tips, tricks or methods for learning how to separate them properly and not just fudge the rhythm?!
EDIT: A recording can be found here: