Whether you are spray painting or spraying...as you move the nozzle back and forth your nozzle has to slow down and stop, and then reverse directions, at the end of each side stroke. Slight variations are not important (except in spray painting auto fenders).
You can use painter's techinque, and cover the concrete more evenly by spraying in a series of overlapping figure 8 patterns as you walk forward.
It does not have to be perfect.
Do not use flat fan nozzles if you move your arm back and forth.