The approach towards revision after completing the entire UPSC syllabus should be systematic. Begin by categorizing subjects into core areas and linking concepts for integrated understanding. Utilizing revision techniques like self-quizzing and mind-mapping ensures engagement with material. Ensure that revisions are regular and cumulative, allowing for retention of previously learned topics. Focus on current affairs and significant events that correlate with the syllabus. Setting incremental goals during revision can help in maintaining motivation and identifying knowledge gaps.