That was my strategy exactly. I failed the Environmental exam the first time. The first time I focused on getting myself organized (tabbing, summary sheets, etc.) and the School of PE review course. After failing, I only did practice problems, concentrating on areas I didn't do as well in. If I didn't understand/struggled with the practice problem, I went back and reviewed the material. I also took several practice exams. Organization and then practice was key for me. I essentially made my own reference manual with equations and appendices I used and organized it by subject matter (I barely used the EERM on the exam). I indexed all of my practice problems and equations/topics alphabetically and had a separate index for each for fast reference during the exam. The prep was grueling but paid off.