Shanghai - Hong Kong - U.S

Hi,

I will be traveling from Japan to Shanghai and will stay in Shanghai for 2 days. After i have a flight to Hong Kong and plan to be there for 4 days and will head back to the US.
Will i be able to get the short term entry visas in both Shanghai airport and Hong kong Airport or would i have to apply for a full visa from the Chinese embassy here in Ny?

Thank you in advance, ive been to the local embassy and they cant answer my question.