I'm sure I'm not the first to think of this but it came to me today as I was adjusting the valves after a lifter and PR change on my 79 350. With my finger over the plug hole I bumped the starter with a remote switch until I felt the air blowing, signifying the compression stroke. At that point I inserted my inspection camera into the plug hole and visualized the piston's rise. Had to go around a couple of times on some of them but it seemed to take some of the guesswork out. Any reason this isn't an effective method?