Shoreham will be my first attempt at at serious dslr photography. I have been practising on the local seaguls and at the model aircraft club where I used to fly. One thing I have had some success with is rather that part depressing the shutter release and allowing the camera to focus, I fully depress it so as soon as the focus is good, the picture is taken. Continuous AF doesn't seem particularly good on fast moving objects.
I too have the 150-500 and find it is capable of taking a good picture, but not wide open at 500mm. I try to stick to F10 or smaller.