It's easy. Run this code from the script console, and it will apply the properties from your script to every scroll bar in the designer:
def fixScrollSpeed(scrollableObj):
for component in scrollableObj.components:
if 'ScrollBar' in component.__class__.__name__:
component.setUnitIncrement(component.maximum/4)
component.setBlockIncrement(component.maximum)
else:
fixScrollSpeed(component)
from java.awt import Window
for window in Window.getWindows():
fixScrollSpeed(window)