China Railways parcel services

I'm from Canada and I'll be moving to Thailand for 1 year, but before I move to Thailand I wanted to visit China for 1 month. I'll be going to many cities (7+) including Shanghai, Beijing, Xian, Hong Kong, etc. and travelling by train between these cities. (My trip will start in Shanghai and will end in Hong Konk) I'll be having 2 big pieces of luggage because I'm moving to Thailand for a year. Now I thought instead of having to carry my luggage with me during my visit in China, I would use China railways parcel services to just ship them off from Shanghai (my first stop in China) to Hong Kong (my last stop in China). My question: Does anyone know how much it would cost approximately to ship two luggage from Shanghai to Hong Kong (or Guangzhou if not possible to ship to Hong Kong) using China railways parcel services? AND will they be able to keep my luggage for me (if so, how much?) for around 1 month until I finish my trip in China?

If you have a better suggestion I'm all ears.