For todays Technique work, the Headstand push up refers to what most of you know as HSPU in CrossFit except its going to start on the floor in a headstand, press out and step down. If possible you may Press out, Hold and begin your HSPU Negative back to the floor. However do not do either at the expense of form. For the Headstand Push up, try to avoid kipping. When pressing Id rather see the feet track toes toward floor than see the back arch. Meaning if you cannot press out, Lower your body in a hollow position toward a push up and press once bodyweight is alleviated, and finish in a push up. This reintroduces the press through hollow of a HSPU better than allowing the back to arch mimicking a wall HSPU. 

A1: 10x1 Headstand pushup 

A2: 10x1 Free Standing HSPU Negative