The blowing grasses is reasonably customizable.. one can keyframe the
turbulence intensity, frequency on the brush node, as well as keying the
other brush attributes: uniformForceXYZ, gravity, random, pathFollow and all
the other attributes. You can create control curves for the stroke and on
the brush adjust curveFollow, attract and max dist( with lengthFlex=1 and
curveFollow = 1 the tubes will stretch with the control curve). The control
curve cvs can be animated or you can push them using particle/softbody/cloth
animation methods. If you really need to use the Maya forces, as opposed to
the built in forces and controls on the brush then the main technique is to
create control curves for the strokes and apply forces to those. One method
uses the deformation of the control curves to push the tubes. Another trick
is to make one or more small control curves(in effect single points) and use
negative or positive curve attract, along with curveMaxDist. Use in this way
the curves are like point forces and you can animate the curve tranlation or
group the curves with moving objects..with negative curve attract they are
thus repeller objects.
Duncan