Ditto on the K-D tool, my hands sing the blues the next day.

Mind you I've only worked on big block wedges, but all I've ever done to change springs or seals was to have that cylinder on TDC, plug out. and using a small bent little screwdriver through the plug hole to hold the valve against the seat to remove the locks with a magnet.

The valves won't drop out of sight with the piston up top.
I use a little rap on the retainer to free up the locks before compressing the spring.

BUT....keep some rags blocking the drain passages before you start!!

Joe