Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Lock On Select
HAIR_TOOL_BRUSH_LOCK
Parameter: Selected Only
HAIR_TOOL_BRUSH_SELECTED
Parameter: Hair IK
HAIR_TOOL_BRUSH_IK
Parameter: Collisions
HAIR_TOOL_BRUSH_COLLISIONS
Parameter: Coll. Radius
HAIR_TOOL_BRUSH_RADIUS
Parameter: Mode
HAIR_TOOL_BRUSH_TYPE
Parameter: Falloff
HAIR_TOOL_BRUSH_FALLOFF
Parameter: Strength
HAIR_TOOL_BRUSH_STRENGTH
Parameter: Width
HAIR_TOOL_BRUSH_WIDTH
Parameter: Falloff
HAIR_TOOL_BRUSH_FALLOFF_CURVE
Parameter: Distance Falloff
HAIR_TOOL_BRUSH_DISTANCE_FADE
Parameter: Distance
HAIR_TOOL_BRUSH_DISTANCE
Parameter: Falloff
HAIR_TOOL_BRUSH_DISTANCE_CURVE
Parameter: Viewing Angle
HAIR_TOOL_BRUSH_VIEW_FALLOFF
Parameter: Falloff
HAIR_TOOL_BRUSH_VIEW_FALLOFF_CURVE
Parameter: Guide Falloff
HAIR_TOOL_BRUSH_GUIDE_FALLOFF
Parameter: Falloff
HAIR_TOOL_BRUSH_GUIDE_FALLOFF_CURVE