Use the first pass to collect marks from questions you understand clearly. If a question is consuming time without progress, mark it for review and move on.
Keep a protected review window near the end. Use it for unanswered questions, calculations you want to verify, and responses marked for review.
A fixed plan is only a starting point. After each mock test, compare where you expected to spend time with where you actually spent it. Adjust your next attempt using that evidence.
Practise the complete three-hour sitting regularly. Time management improves when the testing conditions resemble the conditions in which you need to perform.