There is not any set rule for doing Composition's paper preparation. because Precise and Comprehension contains 40 marks and it is skill based, so you should do practice as much as you can.
And the other portion contains pair of words, antonym, synonyms, idioms and phrasal verbs; and no one can become master in them because there are infinite of them. And the remaning are translation and sentence correction, the skill to tackle them also comes from practice.
In nutshell, what you need to do is first and foremost get good grip on english grammar as it is most important and in whole paper your grammar and way of expression will be checked and it will help you in sentence correction and translation. And then do practice of precise and composition as much as you can and once you feel that you have achieved all skills and you can tackle it then go for other portions. And for antonyms, synonyms, idioms etc. You should arrange notes from a senior because they can give you the list of them which are selected and have good chances that they will come in paper; memorize them and furthermore read daily Dawn and point out difficult words and memorize them, so on day of paper will have good collection of all of them. And trust me it is not a difficult task if you have good grip on grammar then 2 months are more than enough for preparing this subject. Hope my this experience is going to help you alot, and kindly do not follow blindly anyone and the same goes for me too, I am an aspirant like you and what I am sharing is my experience of few months. So, keep asking from seniors and do what you think is a perfect technique to tackle the paper.
Best of Luck 👍