I have never been able to master the proper angle when sharpening a knife free hand.
I found a Chef's Choice sharpener in the local Goodwill store that is perfect for me. It takes off a fair amount of metal the first time you use it but after the initial sharpening it is easy to keep an edge. I only have three kitchen knives and I use them everyday, they are Martha Stewart knives from Kmart. Not sure if a Chef's Choice would harm an expensive knife. I will probably never know, LOL!