I find Kant almost painfully clear (hence the absolute dryness Save the chubby Mermaids shirt; a bit of ambiguity and “humidity” would make reading Kant a little more “delightful” an experience, as well as making his philosophy a bit more profound and in touch with lived-reality). He’s trying very hard to be unambiguous. But, this does mean that every sentence is important, as they are all incremental steps moving in a straight line down the path of a (very) long argument. Miss one key step and you’re lost. The key is mainly the “definition paragraphs” where he creates about twenty concepts that he is about to use over the next ten pages. This is a style particular to Kant (huge definition paragraphs in the front and the “moving right on” pace). For Heidegger, for example, a good trick is to skip to the chapter ahead, where he always provides a summary of the previous chapter which can help you gain your footing. For Nietzsche taking a pair of scissors to the book and doing Burroughsian cut-up is a viable strategy.
For Deleuze, opening the book at random sideways points and reading backwards and forwards can work wonders. Hegel needs to be read like Kant, but in concentric doubling back circles, etc. Taking notes is key. He will introduce series of definitions in little bursts and then start using them right away. If you find yourself reading a paragraph and aren’t seeing how these terms are fitting together, go back two pages; you’ve glossed over a “definition paragraph”. Take breaks and think about it when your eyes start crossing over. The great thing about the CPR is that you can pause, look up from the page out across the room, and try to see what he is talking about in the world in front of you (because he is talking wholly about the world in front of you). The effect of an object upon the faculty of representation, so far as we are affected by the said object, is sensation.