I know many people don't like them due to the noise increase but I have had very good luck with the Vais brake shown here. I had one put on my daughters 30-06 last year and she absolutely loves it. Her flinching is gone and comfort level is way up. I'm having one put on my 7mag now so as to be able to see where I hit better without a spotter.
These do not seem to increase the noise level as much as some others do.