Hi Surik,
In reference to reviewing each question after the test and writing down the formulas to improve in certain areas, that is how I study as well. I find it to be the best way to learn. Just don't keep retaking the same test multiple times because then you just memorize the answers to that test. So keep doing this and moving on after you have the theory memorized for each question.
In reference to your question about how to better study Verbal. I always recommend starting by going back to the basics. Without knowing the basics of grammar you will have problems with all verbal. Even if you know the majority of the basics, there are most likely a few basics you don't have down. Get yourself a book that covers grammar basics if you feel necessary (if you can find some helpful videos as you said you prefer those, go for it). After you feel that you have this down, then I would recommend taking a practice test or some practice verbal work to determine your specific areas of weakness. Focus on those sections and don't move on until they are mastered. I don't know any good videos that I can back up, but I do recommend a book called "English Grammar in Use" (intermediate and advanced levels). Please be aware that almost all grammar books tend to be exercise-oriented and often go into much more detail than what the GMAT tests. In addition, many grammar books do not deal with certain sentence structure issues (e.g. dangling modifiers). You need to cross-reference what is on the GMAT with the book you get. But "Grammar in Use" is probably the best grammar self-study book available. If you don't think this will be useful as you prefer videos, I understand. Personally,while I do enjoy the books, I do best learning face to face by speaking and asking lots of questions. Everyone is different. Knowing what works best for you is half the battle. If you have any other questions at any point please do not hesitate to contact me.
Good luck!
-Evan