+1 on getting a better bow.
Here's a 3 minute exercise I do which improves the sound of my bowing if I haven't played in a while:
-Set the metronome at 90
-pick an open string, I usually start with the D-string
-for all the bowing listed below, use the whole bow. Be sure to go from the frog to the tip.
When you change directions, be sure there are no scrapes, pops or other extraneous noises.
Don't go on to the next number until you can change directions without noises.
Be sure to bow in the sweet spot nearish the bridge for maximum resistance and biggest sound. It should feel similar to the feeling of walking through mid-calf deep water along a beach.
- go back and forth for 2 clicks for few times until the rosin is warmed up (I sometimes wait a couple of clicks between stopping the bow and going the other direction to make sure the string releases smoothly in this stage) then:
- 2 clicks four times
- 3 clicks four times
- 4 clicks four times etc
- etc 5, 6, 7, 8,
- then work backwards - 8 clicks, 7, 6, 5, 4, 3, 2, 1
-if you can get it to two, three or four bows from frog to tip per beat, the whole bass should be blasting out huge notes.
Now, when you go to playing regular quick notes that use 4-8 inches of the bow, you'll find change in direction much cleaner and you'll have a bigger more beautiful tone.
Do this for all strings.