so i decided to revisit the old 220v Fujima pressure washer that's been sitting here unused for a couple of years, but this time w/ a new smaller-diameter hose that's more flexible, and a new short gun (the original was super long which has its uses but is unwieldy for car washing).
i also installed a smaller 0.9mm brass orifice for the foamer (stock orifice is probably 1.0mm). i poured just 2 capfuls of MTX shampoo into the bottle then filled it up w/ water. the foam quality isn't great but is good enough. still a bit runny but stays on long enough for you to wipe down an entire side of the car i.e. you just have foam blast one side at a time. maybe the foam could be improved w/ a better shampoo...
works pretty well as it is. i like that it blasts out a lot of foam quickly. those battery foamers seem interesting but the output seems low, gonna slow down your work...