I've seen pictures of cam damage on RCU. I think Bill Robison had pics of damaged cams. My high time 72 has cam followers that look brand new, right out of the package but the cam has wear.

I don't use the Saito tool as I don't think of it as a feeler guage. I have a set of good ones from Sears. You use them to feel the valve setting as you tighten it down. But, I've never used cellophane or other trick things when feeler guages do it right and are pretty cheap to begin with.