You should not spend more than three hours prepping a lesson, man. Have some faith in your mastery of the material itself and your ability to teach it.
Having said that, here are a few pointers that might help you streamline your preparation for each lesson:
1) Highlight keywords, not whole sentences or phrases in the bubbles. The one exception to this rule is the highlighting of questions that you're supposed to ask the class.
2) Use the TEL as a PROMPT for your own explanation of the concepts. Often the TEL has good explanations and illustrations of concepts but not always. I think that the visual aids (figures, graphs, charts, etc.) are excellent in the TELs and, therefore, you should definitely include these visuals in your lectures. However, not all of the definitions and explanations of concepts in the TELs are great; consequently, I often substitute easier definitions (no fancy words) and more intuitive explanations during my lectures. When in doubt, anthropomorphize things--i.e., treat subjects of discussion (e.g., molecules) as human beings. For example, I often refer to halogens and other highly electronegative atoms as electron extorters. Sounds stupid, but it works.
3) Use an orange highlighter for questions, a yellow highlighter for everything else.
4) Use a red pen for the passages and the questions. Don't highlight any of the explanations for the answer choices, just write a brief rationale in your own words next to each answer choice (in red pen, of course).
5) Ask the class a lot of questions during the lecture. Get them involved. Instead of giving them the definition of induction, ask them for a definition. And make sure that people give a definition that reflects their own understanding of the subject, not some BS textbook definition. Preparation for a lecture that is decidedly Socratic takes less time than preparation for a pure presentation.
Hope these suggestions help a little.
