Whisking egg whites by hand using a hand whisker takes around 18 minutes of whisking which can be hard work.
You'll give your wrist and arms a good workout by hand whisking the egg whites because it takes a lot of effort.
After about 5 to 8 minutes you should be achieving the results of whisking the egg whites by hand and after 18 minutes the results should be fully achieved.
So be prepared to work your arms really hard and wrist to whisk egg whites by hand.
You could also just use an electric mixer to mix the eggs up and whisk them which will do the work easier and faster.
But if all you have is a hand whisker then just be prepared to whisk the egg whites for 18 minutes by hand.