I have the Skybolt fasteners, but I assume they work the same. This is one of those things that are a pain in the butt at first, but gets easier with practice. I use one of those micro flathead screwdrivers and pry them off using a twisting motion at the point where the break in the snap ring is. Hint: Because the cut in the snap ring is on a bevel, it will be easier to pry off by lifting on one side of the ring than the other - experiment a little and you will figure it out. I think it took me something like two hours to get them all off the first time when I was getting ready to prime the cowl, and blood was spilled. Recently did them again before final paint job - down to about 15 minutes.
Be patient - it requires a lot more technique than force.