I also have a brother and they make a "free-motion open toe quilting foot" it's great and I did change my tension but later found I went back to the set tension of the factory 4.2 because problem I was having was not the tension it was me. Like the earlier blog, you have to figure out the speed and the hand movement to be matched together or you will get that bad tension look.
Brother SA187 part number
Hope this helps.