Help could not take screen capture with Stratosphere 2

Lots of pages say that you can take a screen shot on a Stratophere (I) by pressing the Home and Power keys together:
Samsung Stratosphere: How to Take a Screenshot

That works on my Stratosphere I.

However I had a Stratosphere II for about a week and the home-and-power key combination did not work for taking a screen shot. I called Verizon tech support and they had no idea how to fix it.

I found one other thread:
screen shot on samsung stratosphere 2?? - Android Forums at
where someone reported the same problem, and they said they discovered some trick involving the volume keys; they said they couldn't reproduce the trick successfully, but advised the reader to "practice and it will eventually work" (!).

Has anyone successfully taken a screen shot with a Stratosphere 2 and knows the key combination that will do it every time?