I also struggled w/ the installation of the spiral sanke rings. The method that I've finally become skilled at works well for me and I will share. All that is needed is a small pair of channel lock pliers (say 6"0). A regular pair of pliers would probably also work but the offset working angle of the channel locks helps.
All you do is get the spiral ring started by hand which is usually close to 1 revolution. The point at which it becomes difficult is when the spiral ring is doubled in the retaining groove. Position the remaining free end of the ring inside the neck of the keg adjacent to the retaining groove.
Begin forcing the ring in the groove w/ the pliers by squeezing between the snap ring and the outside neck of the keg, well behind the unseated portion . Slowly proceed around the keg neck w/ the pliers and the ring will spiral into the groove.
Only move the pliers 1/8 - 1/4" w/ every compression. If the ring seats in the groove, great, move forward and squeeze again. If the ring is stubborn, back up and make sure the preceeding portion is full seated!
W/ a little practice it's a 30 second job.
I actually have grown to like the spiral rings in that they are compressing the large o-ring upon installation. Not sure a regular snap ring will compress the o-ring seal as well.
Good luck, it's tricky at first but will become easy.
Mike