Face the opponent properly first before you hit. Don't chase the opponent's hands. Just hit the central axis of the opponent. Flowery movements are not good in Wing Chun. Simple connected movements will do.
Sore shoulders come fom trying to fight against energy.
You should not lift the Bong sau , it should spiral forward with minimal shoulder use. Try to use the concept of neutralizing force along the tangent of a circle. The circle can be horizontal, vertical or diagonal. Many people apply their energy at the wrong moment. Try to feel when is the best time to apply your energy.