Not looking very hard because we have quite a few guides on a number of things here on this leaderboard lol to answer your question that's in the title of the forum post, strafe running is just running at a 45 degree angle, that's it. To answer the question in your post, just rewatch the run and use a stopwatch of some kind if you really need to. Or while doing a run, use a program called Livesplit. It's what most speedrunners use to time their runs.