In the spirit of the Great Cortot editions, I made a modest exercise from bars 17-18 that you can perhaps use for other bars. I took a glance at Cortot's op.25 edition, and this exercise was not included in his "pre-practice lecture" on this etude, but I am sure that somewhere along the line he said something from which I derived this exercise.
My music notation program does not allow me to conviently enter fingerings, so be sure the fingering is exactly the same as it is in the music. The notes are in a different order but use the finger correspondingly in the original version.
And remember that 5 doesn't reach to cross over the thumb, rather it is a lateral movement of the hand that accomplishes that.
(see attachment)
I would print it out and write in the fingerings.
Also, the reason the pattern is repeated so many times when it changes into straight 16th note pattern is, I found it somehow helpful when dealing with passages like this, where a mental block can easily arise, to change the points of accentuation, so that your mind isn't always obsessing about when to change fingers in the same place.
Sorry that's not very articulate but maybe somebody else can say it better.
Walter Ramsey