My solution is to put a backlight shortcut (namely, \Windows\Backlight.exe) on the right softkey of my Today Screen. That way, without being able to see the screen at all (which is often the case when outdoors here in South Florida), I can press the right (red) hardware button (takes me home), tap screen area just above it, and then a few right navigation presses brings up the brightness. Works for me just fine. Only need my left thumb, holding phone in left hand. I have the new leaked Sprint ROM, so used the new version of KeySwop by Vicsoft, freeware, now compatible with WM v6.1, here:
http://mobile-sg.com/software/?p=KeySwop&platform=ppc
Hope this helps, MrG