I just completed the removal of the inner springs on my heads in prep for cam break in too. I only did the drivers side while bolted down as the passenger side head was off to fix a bad rocker bolt insert in my head. I used a compressor made for removing springs while heads still bolted down. I fab'd up a spark plug air fitting using my comprression tester and put 120PSI in the cylinders. Becaues I have dual springs with the damper (like your pictures above) the compressor only grabs the outer so you have to overcome the inner spring pressure to remove the locks. With a sharp rap on the head of the valve they keepers losened up and I was able to remove it no problem. Actually it was pretty simple. Biggest problem is not to loose the keepers if the pop out.
Like you I am using the "belt and suspenders" approach to cam break in. I removed my inner springs, plus I am going with a high
zinc oil (in my case delo400 10W-40 diesel
oil), and to add a little extra insurance I am using the GM EOS (engine
oil supplement) too.