As above, it is a tedious job.

We usually do mine with all the components clean/dry. Assemble with cam in, and followers, then tighten down the rockers to the correct torque setting and measure.

Then, with the Newman adjusting tool in the vice, adjust each follower by removing it, adjusting it, locking the locknut and refitting it to the engine, reassembling and re-torquing, then checking the clearance.

Once you are happy with all the clearances, then I would suggest removing everything, cleaning it all up again, and lubing up the cam/followers etc with a suitable lubricant, before putting it all back together one last time. I usually pour oil into the head too before putting the rocker cover on, but immediately before I plan to start the engine. (obviously make sure that you don't put more oil in than the engine needs).