I can help you here as surfactants are in my area of chemical expertise as they are used extensively in Mining and oilfield as well as personal and home care products and of course car detailing products.
The reason for applying as a foam is to get residence time (dwell time) on the car so the surfactants stay clinging to the paintwork doing their pre wash duty. However this is NOT the optimum method for applying surfactants. Many people do indeed use garden sprayers but get the dilution wrong so it simply runs off the car and does not do its job, but if you get the viscosity correct so it still clings to the car it gives a far more concentrated layer on the paint and does a more in depth job. With most quality products you need to have a solution strength around 4% - 5% but could possibly push this a little higher but after 7% you will definitely start to strip wax or whatever LSP you are using.
Surfactant technology has moved on massively so there is no need for the foaming variety except in a very limited number of applications, In fact R&D over the last 5 years has been focussed on stopping foaming in surfactants so without shadow of a doubt in a few years time snowfoam will be obsolete because there will be no demand for the base surfactants in it. There are some really good non foaming pre washes out there already with high powered neutral surfactants not cheap but do an extremely good job.
