Advice

Hi friends I am a CA Final student. I hv completed my articleship training. Further I hv taken exams in Nov 2015. I hv taken training from a mid sized firm. I would like to go for practice in future but with specialization in the field of international transaction or mergers N acquisitions. I would like to know how to get entry to big firms to such departments.. Whether it is feasible..! What all I shud do to get entry... Any advice..?