Also not an instructor, but I'll answer anyway:
If you have to divert for real, it's likely to be a high-stress time. One of the most likely reasons is bad weather. Another is a technical problem which means you'd be happier on the ground. Under these kind of circumstances, the last thing you want to be doing is worrying about a wind computer! Not to mention that it's a bad idea to have your head inside the aeroplane doing calculations at any point during the flight.
A rough estimate in your head will probably be accurate enough. But my instructor taught me a neat little trick. On my plog, I have a "wind star" - an 8-pointed star for each of the 4 points of the compass as well as the 45-degree points. Before the flight, I work out the drift (degrees left or right) for each of the 8 points. Then, for a diversion, pick the closest point and apply wind drift.
Quick and simple - it won't take your mind off the task in hand, or your eyes away from your traffic scan.
FFF
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