the most important thing not to do when practicing this etude is to be tense. it will undoubtedly bring tendonitis if you practice it the wrong way hour after hour. I think the best way to go about tackling this etude is to absolutely master the right hand fingering first---without the left hand, and importantly, without the chords aiding the right hand flow. if you learn the chromatic scale with out the supporting chords in the rh, your ears and fingers are more easily trained to understand the continuity of the legato passages throughout. the chords can be incorporated later and be played as simpy supporting, background material to the chromatic scale. when playing the chords, don't pound them out but almost pretent that the aren't there, that they are just a natural part of the chromatic scheme.
the left hand, of course, is a strict contrast to the right as it is to be played staccato---aim for a very light touch, fluid elbows, and a sound that goes up with gravity, not down with it.
once you put the r and l hands together, play very very slowly, and in small sections. when u master a small section at a slow tempo, you can gradually increase your speed always keeping in mind the lightness of your touch (whether u play legato or staccato) and the relaxation of your body.
good luck! it's a fun piece if know how not to freak out in the process!