<p>I have an a7 II. I chose it for the IBIS to use with manual FD lenses. There are two situations that come up with focusing. Either I'm running a zoom lens on my metabones adapter, or I'm running a prime. On a zoom, the best way I find to do it is zoom in to maximum, focus, and pull out to frame it, and snap the shot fast. The second way to do it is, if the zoom is low level or it's a prime, map a button on my manual mode of the camera body to be "focus zoom-in preview" or whatever it's called. It will blow the preview up to a small section of the center of the image, and let you get a crisp focus on an eye, or an animal, or whatever you want focused.</p>
<p>I shoot in manual on my a7 II. I have the fore wheel set to shutter speed, the back wheel set to aperture (not used in this case), and the rotary select wheel set to ISO. When shooting with FD glass I set ISO to auto, manually select shutter speed, and rotate my f/stop ring on the lense to what I want. With the light sensitivity available on this body, I can often put it at much higher f/stops to get better focus on my subject, even if I'm a little off. That way I can "best guess" it and it will still come out okay.</p>
<p>If you can, ditch the a7r and get an a7 II. the in-body image stabilization will really lend itself to your older manual FD lenses. It breathes new life into them, makes it easier to take shots with slower shutter speeds, and is a lot more consistent with indoors or low-light than hand-held shots on my A-1.</p>