First of all, do you really think it is necessary to know everything about the passage for GMAT? I do not think so. I might read a CPA prep article word by word. However, this is a test, which means that you do not have to hang over the details at all.
In my reading, I will have a list of things I will be looking for: conclusion, argument, supporting premises, structure, reasoning, and last and least important, details. To me, as I said before, RC is just a stretched CR, without more details and extra layers of argument. So get the essence of the article first, and it will help you understand faster and better. To achieve that, you need to think while reading. Not think over the details though, but what is the conclusion, what is the argument leading to, what is the reasoning, structure, is this the author affirmative, etc.