Adding a weight to the head of the brush means that you only have to slide the brush back and forth.
We add a handle extension so that the pushing hand can be moved around:
Higher up, towards the main shaft of the handle, for slippery surfaces, or when you want to push down harder; Lower down for high-friction cleaning tasks or when you want to take it easy for a bit.
Running at a head-weight of 15 pounds made cleaning my deck (coefficient of friction about 0.3?) in preparation for this year's sealer about 2-3 times easier than with a standard scrub brush.
Note, however, that because the heavy head discourages you from brushing fast, you might not get done any sooner.
Construction is pretty straight-forwards. Dimensions of the 1" PVC pipe are given in the image notes.
To use, simply assemble the brush with some weights on the handle, and go scrub something.