Pseudofly
Pseudofly is an advanced hammerfly technique similar to speed fly, in which the two tees never come into contact and the hammer tee hammers very quickly. With enough practice, a tee (or tees) can pseudofly up, down, and sideways, at will. Pseudofly is generally easier with a dummy, but can also be done with another player as well, although requires great coordination between the two.
Pseudoflying with a dummy
When pseudoflying with a dummy, it's important to control the rate at which the dummy hammers. Therefore, auto-hammer is not enough. You can bind a key to have your dummy hammer at will using the following command:
bind x "+toggle cl_dummy_hammer 1 0"
Once you have that set, you can start pseudoflying.
It is possible to start pseudofly in the air, but it is easiest on flat ground. Start by standing next to the tee, then have the dummy hammer you at a fast rate, hook him at the same time, and start moving in the opposite direction in which you are positioned from the dummy.