Again, some great pics..
I have always used the viewfinder. It's not brilliant but it shows enough to know that you are focussed correctly (or thereabouts). Having it jammed up against your face helps to keep it steady. As with the SX40, you have to have your eye in a certain position for best results when using the viewfinder and ensure that the diopter is set correctly. I wear specs, but find it better without them.
I have tried the' Framing Assist - Lock' button but by the time I've found it, the bird is gone or I have lost the subject. If anything, I tend to be fiddling around with the 'Framing Assist - Seek' button above it which I find invaluable.
AndyM