Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Enable
HAIR_RENDER_TAG_ENABLE
Parameter: Auto Time
HAIR_RENDER_TAG_AUTOTIME
Parameter: Start
HAIR_RENDER_TAG_START
Parameter: Stop
HAIR_RENDER_TAG_STOP
Parameter: Mode
HAIR_RENDER_TAG_MODE
Parameter: As Fill Hairs
HAIR_RENDER_TAG_HAIRS
Parameter: Length
HAIR_RENDER_TAG_LENGTH
Parameter: Scale
HAIR_RENDER_TAG_SCALE
Parameter: Count
HAIR_RENDER_TAG_COUNT
Parameter: Segments
HAIR_RENDER_TAG_SEGMENTS
Parameter: Restrict
HAIR_RENDER_TAG_RESTRICT
Parameter: Limit
HAIR_RENDER_TAG_TRAIL_LIMIT
Parameter: Trail
HAIR_RENDER_TAG_TRAIL
Parameter: On Death
HAIR_RENDER_TAG_DEATH