I am sorry to disappoint you but there are no shortcuts when you are preparing for CSS exams, as you are short of time then the best strategy would be to buy revision aids which specifically deal with one question at a time.

For political science I, you will have to study the works on plato, aristotle, bentham, mao, locke, hobbes, etc etc. The list seems exhaustive but you can cover all the theories within a day, all you need to know is the basic idea and the pros and cons of their theories.

The second part of the paper is intended to examine your knowledge on contemporary aspects of political movements such as public opinion, liberty, propaganda, pressure groups, democracy, dictatorship. If you have been reading the newspaper and thoroughly following the world events then you shouldn't be to worried about this section.

Political Sci II, You have to cover six constitutions, this part is lengthy, and quite tedious to understand but still you shouldn't lose hope, work hard as you can and try to cover many constitutions as you can in some detail.

As far as the essay is concerned, it is best to draw outlines as opposed to writing full essays because time is very limited, and you should divide your time effectively, and utilize efficiently.

Keep working hard and all the best!