Don't think there's a right or wrong as to when whether to use snow foam before or after an initial rinse. Technically though, the correct method would be to use a citrus pre wash first, then rinse then snow foam. 
Whilst you do want some cling, you actually want the foam to work its way off the car on its own which is why when you see these ridiculously thick foams whilst it might look great, it's not really doing its job properly...
My 2 jobs this weekend.... Maintenance wash on the GTS and full deep clean on the BMW - this was a serious task as not been properly washed in 3 years and 4k miles! You can see the snow foam literally dripping off which for me means its working.
Great work Jim. Both look superb.
I prefer to use snow foam first followed by Citrus Pre Wash. I’ve always favoured using VP snow foam (a relatively runny snow foam) before the Citrus Pre Wash as that’s logical order to me to get the most effective cleansing out of both pre wash products, use them to their individual strengths. I know some prefer to use the two the other way round with citrus pre wash first then snow foam, but tbh I never quite seen the point of that - imo that way round reduces the action and effectiveness of the snow foam, on the initial layer loose surface dirt, and is a bit of a waste of the deep cleaning attributes of the Citrus Pre Wash on the more stubborn clingy grime. The strength of a good snow foam being to initially soften and encapsulate as much of the loose dirt, grit and debris as possible and then carry it off the paint/wheels without the need to touch, the remainder being swept away with the pressure washer at pre wash rinse stage. So for me it’s snow foam first (applied via a lance to dry car) dwell and rinse off with PW. Then VP Citrus Pre Wash (applied via a snow foam lance) sprayed on and left to do it’s deep cleansing work on the stubborn non loose dirt still remaining on the paintwork/wheels, the stuff that snow foam simply doesn’t impact on, then PW rinsed off. Ime this leaves the car bout 80% clean having massively reduced what the bucket and mitt wash has to tackle which means all that is needed to follow is a very gentle mitt wash and therefore greatly reduced risk of wash inflicted swirls at the 'touch' stage of cleaning. For me, in that order, it’s a winning pre wash double act. All personal pref though.
