There's actually no real separate or distinct strategy for passages with harder content - all of the usual strategies that apply to any verbal passage will help improve your performance, even on really hard passages.
You've got to remember that what makes verbal hard is not the content of the passage, and not even the wording of the questions. What makes verbal hard is when the trap answer is really tricky and really "close" to the right answer.
If you're having trouble focusing on a passage and extracting the main idea, and opinions and contrasts, because you just don't understand the content, then at the very least try to focus on the tone of the passage. "Okay I have no idea what [this long winded crazy phrase] means, but the author seems to like it." When analyzing the questions, stick as much as possible to that tone. The EK verbal workbook has a good exercise on this.
Good luck!