I think walking meditation is often done incorrectly. I do not believe it should be about pure focus on the walking and more about sustained awareness of the world.
When you are walking, try to establish a constant rhythm with your legs; this keeps your dopamine latched and ticking over.
Allow your hands to drift and your eyes to float. See everything that is passing you by with a relaxed awareness, while keeping a loose attention on your hips and legs.
The aim here is to train yourself to experience your entire sense-world and to be in flow with the universe, not to achieve a state of complete focus.
Let your face and jaw go slack and let your eyes drift half closed while focusing on sounds and the smells for a while. Feel the taste of your tongue against your teeth and allow the eyes to drift open a little more and take in the world.
Brush your fingers against the plants you walk past and let your hands float in the air like water. So many cultures have similar hand motions: the Hawaiian and Arabian dancers, the Indian mudra, the aikidō master, the midnight raver.
These waterhands will raise your serotonin levels, make no mistake, just like when you were a kid and held your hand out the car window to ride the currents of air.
Walking meditation is when you ride the current of the universe. The focus can come later.
This is a good time to text yourself for some level 1 processing and compiling.