I stuck with theories in part 1 and attempted every answer with respect to theories. In part 2, I just prepared for argumentative style of answering questions. I did not cram, just read the facts and attempted past papers. Again quotes and theoretical references help a lot. Use any book but avoid JWT's book by Ikram Rabbani. It is truly horrible. JWT have published another book for IR. It looks much better if you want to try it out. However, use the FPSC recommended books as much as possible and use the internet as well (YouTube).