Cheer up, you'll get there Most of us take at least half a year to develop a proper technique, and then some more time to fine-tune it. The chin is often the hardest part, for the reasons 10Pups mentioned. Also, sideways growth in the neck is a very common phenomenon and has many people puzzled.

To reduce the irritation, I think you'll have to reduce the passes and pressure. Use the lowest angle that you can get, with the spine (almost) touching your face. And like 10Pups, I use a slicing motion rather than a pure scraping one.