Valve spring removal ???

I started with the air compressor approach last time and didn't like it. With piston at TDC, it would sometimes flip the crank under pressure, and throw the socket wrench if I forgot to take it off. I was also scared I might lose air pressure and drop a valve. I ended up just bringing the piston to TDC (checking with wire). I could then let go of the valve and the piston would keep it from dropping far. I could pull it up with my fingers, or with a magnet. I had fairly mild springs (130 lb closed I recall), shimmed as needed. I could just barely slide the keepers in on some. With thicker springs, you might need to jam the valve up tighter to get your keepers in, so might need the rope trick. I am glad I didn't since that would be tedious.

If you use air, my Harbor Freight compression gage kit made connection easy since they have stub hoses with a standard quick connect. You just fear what would happen if the quick connect wasn't secured and the hose pops off. I would put a strong magnet on top of the valve stem just in case.