Easiest way is to set up a dial indicator on the REAR of the camshaft, after removing the cup plug that closes the cam tunnel at the back.
Install the cam sprocket, cam chain, cam button, retainer, etc. Bolt up your timing cover, use all the bolts and torque as required.
Reach through the lifter valley to push the cam forward and back. The dial indicator should show the cam button clearance. Generally, there's too little, and you'd (remove the timing cover for access, and) progressively shave/file/grind the tip of the cam button to get it where you want. A few thousandths is fine. As I said, the OEM system results in about .002--.003 clearance. I bet anything up to .005, maybe .007 is acceptable, but then I've only installed one cam button and that was twenty years ago. Maybe more.
I think that if this were me, I'd degree the cam first. Then set the clearance for the thrust button. At whatever point I felt that the clearance was right, the timing chain, the cam bolts, the button, the timing cover are all torqued into place; all I have to do is pop in a cam-tunnel plug at the rear, and go on assembling the engine.