I didn't really do much specific CARS practice - I did all of the Khan passages, maybe 1/2 of Next Step Strategy and Practice, and the QPacks. My scores have pretty much been the same since I started. I've done all of my passages with a timer so maybe that helps me intuitively know when I need to speed up or when I can take my time.
I read the passages all the way through, then look at the questions. I've been making extensive use of the highlight function, which I think helps me stay on track better. I just highlight pretty much anything important as I go along. This helps reduce spacing out. I don't think this is the optimal way to approach CARS, but it works well enough for me and I'm not going to change it at this point. Different things will work better for different people.
I skip passages all the time. If I hit a dense passage (especially the philosophy ones), I'll usually skip it and come back at the end. I try to make the call ASAP on whether I'm going to skip or tough it out. Reading halfway through a difficult passage and then giving up wastes a ton of time as opposed to just skipping it right off the bat. You also waste time "re-orienting" yourself when you come back to a passage, so it's best to have not invested anything in it.