I know this piece quite well and have already played it. My advice to you, is to shake all the chords throughout your whole arm rather than just the fingers. It makes it much easier to play the piece, and your fingers don't get tired. Also, play this piece SLOWLY untill you get all the notes right. Then begin increasing the tempo little by little, and when you come to the point you start messing up, go back to your previous tempo and start again. It will take a long time untill you can play it (took me about 5 months untill I could play it right), but if you work slowly and steadily, you'll have no problem playing it.