This takes a bit of patience and practice ,

With sparring partner or friend practice just relaxing your arms (not necesarily out and in a fixed on guard mode either ) just whatevers comfortable and freed up ; so you can concentrate on other things flowing together.

Now just practice letting his blows come through but you simply lean back out of contact and then as you straighten up follow his glove back with your own attack. Follow the elbow back and go low OR follow the glove back and go over it ,wherever the opening occurs.

This allows you to set your visual skills into the correct timing mode.

It also sets you into a rythem whereby your attacks will be harder to see comming for him due to his own retreating movment ,therefore more devestating once you put it into practice in real ring terms.

HE has to work in with you, you both just remain in a fixed stance to begin with and add stuff and get faster as you go along so your reactions catch up to your vision and visa versa.

After a few months of practice you can bring other footwork into play ,but for a start begin at the start.

Swap around so you both a get the appreciation of the exersize.