I did it by taking the DAT destroyer and then not scoring my answers. One of the best things I did was ignore if I got the answer correct or incorrect. If when answering I felt an answer was too much of a 'guess' then I skipped it and just learned any information contained in the questions and answers (even if I got the answer right). If the answers had something vague or I needed better understanding I went on wikipedia or did a google search. After going through all of DAT destroyer this way learning the information, I went back through again and got a great score on the DAT Destroyer, practice tests, and actual exam. Better to go through excited about learning than driven by fear and stress of wrong answers.
As for when to take the DAT, I had great success by doing it earlier than later. I took the MCAT as well in the summer and I gave myself about a 4 month time frame. My studying effort inflated to fit the 4 months and in reality most of the studying I did was in the last few weeks. I used this lesson and gave myself 2 months for the DAT. My effort fit the time frame and I avoided the miserable lingering stress of having a long deadline.
As for ochem, I imagine it could be done before taking the classes. Some of the concepts will be new but with the right approach it is reasonable. Fortunately the ochem in the DAT is very straightforward and has soft tricks. There is a limited amount of information to memorize for this section. If that information is memorized then the whole thing will be easy. If one memorizes the information in Chad's videos and DAT Destroyer ochem section, it will be a breeze.
