I'm not entirely sure why you cant see it on a ccd tbh, but yes using a EP is pretty good and simple. It just has to be defocused a little, and the rings may be very fine or almost impossible to see depending on a number of factors (Seeing being one of them as Mark mentioned). I always rake outwards but it doesnt really matter. I use a fairly bright star, I find it easier to see if the star seems bigger through the EP (As compared to trying to defocus a tiny dot that is a star).
As for the secondary offset, I would agree on just using a ruler or vernier for it. I am not sure if in the airy disk the secondary should appear offset, I think it should be in the center regardless. Someone else may know better than me
