Visiting Huanglong in October and wants to know whether any direct bus to Songpan after 3pm. from HL

No direct bus from Huanglong to Songpan, as I know. The bus back to Jiuzhaigou from huanglong will pass through Chuanzhusi. You can get off there and then to Songpan. The bus leaves from Huanglong at 3pm, but the time depends on the driver. So, better to confirm the bus time in advance.