I just started learning the Rachmaninoff transcription three days ago, so I can tell you the most important preliminary step is to figure out fingerlings. In my opinion, 1313231etc style fingering is the worst for this piece. Experiment with crossing the thumb under the fifth finger for some of the longer scales. For practicing, my advice is to practice lightly using just your fingers to play each note, while saying close to the key and letting your arm follow relaxed. Hope it helps.