Control isn't necessary - I'm not sure why it would be specified. On a laptop you might have to hold the Fn key to hit PrtScr, but aside from that it's two fingers to hit 'Right Alt' and 'PrtScr' and the other hand can mash r,e,i,s,u,b.
Maybe it's easier in saner keyboards.
This is the layout that I have (and the only keyboard layout I'll ever buy, because every other throws the pipe key and backslash in a random spot along with randomly sizing the enter key)
http://commons.wikimedia.org/wiki/File:ANSI_Keyboard_Layout_...