||The way I do it is to align the sprockets so that you can put use a socket and an extension to put the socket on the bolt head behind the sprocket.
Then I have someone hold that for me so the sprocket that will 'push' against the extension cannot turn. I proceed to tighten or loosen the cam sprocket as necessary.
When I did this while during my timing belt install, it just seemed so easy. Once the belt was fully on, I rechecked the tightness in the same fashion by simply having someone (my wife) hold that socket and extension on the bolt head right through the cam sprocket. I could easily use my other wrench (the 1/2" drive torque wrench) to tighten to spec.
That was a few years ago, so I'd have to see it again to give totally exact details, but as I remember it, after I was completed with the belt job, I was happy I did not spend the money or time fabricating some 'tool' for this job.