Thanks All.
As for how many days, I spent ~3 months for prep. I tried to do 2-3 hrs daily with some extra time during weekends.
For verbal, the only thing I would suggest is to study official guides and manhattan SC guide. Read a chapter of Manhattan SC, and do the questions for that topic from the official guide. Study the answers, even the ones you got right. After you are done, do the questions once again and try to find out all the errors in all answer choices. The Manhattan guide has a problem matrix at the end which is helpful for this.
For critical reasoning,
OG 12 has many questions with bold face and some of the newly added questions are also lengthy, so I guess
OG 12 represents the latest types of questions for critical reasoning, so it may help to study from there.
For reading comprehension, just practice a lot. Read everything you can, whenever you can. Try to translate the passage into your own words as you read it. This will help you understand the passage and then answering questions will be easy.
Hope this helps ..