I can only further stress what Ken has said; my bow arm kind of sucks though, so I am not qualified to give any real advice, but... practising the extremes, and practising only one particular thing at a time rather than a whole bunch of things - even if it's as simple a thing as just concentrating on using your arm weight instead of pressure - will make your 'normal' playing sound better, regardless of the dubious musical qualities of your sound during the exercises. Also, if you are already blessed with good habits in the left hand, it will still do what you want it to, even when you are concentrating fully on the bow (arm).
I remember playing Findeisen's method helped some; there are many exercises for bow disposal there. There is probably good bowing etudes in every decent method.
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