nVidia Optimus - Any way to manually switch between GPUs?

Apologies if this is an intensely stupid question and I've missed something blatantly simple, but so far I haven't been able to figure it out.
I just got the Asus N43 (i5 460M, nVidia 435M), and while I see an option in the context menu to launch an application directly on the discrete graphics unit, and I suspect it would also automatically switch to it under load (haven't yet hat the time to try a game out on it), I haven't found any option to switch between integrated and discrete manually and independently of applications.
Like, if I'd just like to have it running on the 435M all the time for whatever reasons.
Power4Gear lists some power plans for the Intel integrated graphics, and there's also a dedicated control panel for it running in my taskbar, but neither seem to have any options to switch to the dedicated nVidia GPU.

So where should I be looking?