My old man thought the same as you, ...you'll find that after snow foaming & jet washing it still won't be clean unfortunately. It will get off some of the road dirt/grime but ultimately I still think your car will look unclean once it drys.
Best thing (imo) is to; jet wash, snow foam, jet wash, two bucket clean/sheeps wool mitt, jet wash and then leave to air dry if you don't want to chamois/towel dry it (you will no doubt get water marks though still).
See what the others say too.
Should be OK if wash my car after rain using 2 bucket method as the dusty road will turn to muddy road (not helping either as i will need to drive on the road to work)!! I jet washed my car 2 days ago, just with Citrus pre-wash soaked for around 1-2minutes, then jet washed with Vax PowerWash 3- 2500W. The pressure did a pretty good job removing most of it but as you said, not 100%. I think i can live with that But when its dry and windy, it's like living in sahara hence my concern that when my car is wet (from jet wash), the grid/sand dust will stick to the car before i start the 2 bucket method.
At first, i decided not to wash the car regular and just go to my local Morrison for a quick jet wash once a month. But having a zed which looked like it had just been on a rally on a daily basis, I just can't stand it and something had to be done! As clean as possible with minimum damage to paint work is what I'm aiming for now =)