I have used Charles Danner and I know a lot of well known dealers (one of them referred me to him) have used him in the past. I sent him the barrels from a few Parkers and was very happy with the results. He is a very good rust bluer and he can also fix dents. He is fair and honest and doesnt take forever either. Here is a link to his page.

http://dannergunsmithing.com/page002.aspx