Since first starting to learn the piece, I've been having trouble with the end of the first run on the left hand, specifically the first 3 notes of the last 6 notes (C# C B C Bb B). For those notes, I use the following fingering: 2 - 3 - 4 - 1 - 3 - 2.
The trouble I'm having is with the 2 - 4 - 3 bit, where my 4th finger feels really week when I play it fast, and I have to focus a lot to make the note noticeable.
So my question is: are there any "tricks", drills or techniques that I can use to overcome this?