Hi David, I am surprised you are getting uneven developing with the brush. What I do is place the tray lenght wise and move the brush up and down continously. The brush is touching the film and you have to make sure you brush on the edges also. get a one size bigger tray and hold the film by one corner and move your brush in a steady manner. Keep the same rythm and you should be ok.
When I do it by inspection I try not to take the film out of the developer I am afraid oxidation would cause streaks. HAving said this I do it for some negatives and have never seen streaks or uneveness.
I guess the first thing to try is to make sure the brush is actually touching and removing the developer if you are just passing the brush on top of the film without touching it can cause this problem.
Hope this helps if not, let me know and we will work the problem, I have messed up in all possible ways so I am sure we can arrive at the solution.
BTW what temperature are you using? this might be somthing you can look at also, if too high then it could also be a problem.