I have a coconut tool which is a handle with a stainless steel cutter which you twist into the eyes on the coconut. The biggest problem is that the stainless steel cutter is frequently too big for the smaller coconuts and it is damn difficult to get it into them. I found a drill works better for smaller coconuts. Empty the coconut water, I keep that and then bake the coconut in the oven for an hour. Then it can be easily cracked open and the shell comes away from the flesh quite easily.
Without baking it's a real pain getting the flesh away from the shell.