Well it wont hurt the monitor turning it off and on everytime you are going to be away from the monitor. If it's for a few minutes at a time then is it really worth it?
I turn my monitor off everytime and it works just fine, it doesn't hurt it and is the best way to do it imo.
However I always lock my computer with windows key+L or ctrl+alt+delete to lock it.
or here's the short cut,
%windir%\System32\rundll32.exe user32.dll,LockWorkStation
I'm sure there is a way to do as you said above with being able to quickly force it into power save mode, but nothing is wrong with shutting it off after use