Hi karovd, I would stay away from Barron as there has been many negative reviews on that including my own. I used their material and really did not like it. I would suggest you to stick with the OG but the 20% SC that you missed and % CR/RC that you missed, you should go through them in DETAIL. I considered the OG my own GMAT bible and you should know it inside out. Try not to know the SC correction by heart. Instead, you should know how to explain each and everyone in your own words. I got about 95% SC correct in OG and the ones I missed, I knew exactly how to explain them. I knew also how to accept and reject each answer choice. Your SC skill is not to be neglected because the truth is that in most of the GMAT cases, you will start off with 1 or a few SCs in a row. Should you miss those early ones, it will undoubtedly impact your score.
As far as RC and CR are concerned, if you ran out of material, I would suggest you to use the Arco LSAT book. I used that and I found it relatively good and will it certainly sharpen your RC and CR skills. But remember that you have to analyze the CR and RC in an excruciating
way. Do not simply go to the answer key and say: "Oh, it was A, I got E. Let's move on". That is the worst approach and will only ensure that you know the answer, not the concepts. This is a painful process, let's admit it, but it is the ONLY way that will improve your verbal accuracy.
Akamai once taught me this and I commited it to memory.