Chemical and nitrogen flushes have different purposes. The chemical flush is to remove oil and contaminants from the lines and coils. Dry nitrogen sweep is to blow out any moisture in the system.

Ideally you'd do both. In reality, I typically use a solvent flush followed by compressed air. I have a desiccant dryer on my air line, so the air is quite dry. I typically use Acetone as my solvent of choice. $13 for a gallon from your favorite home improvement store vs about the same for a pint of "AC Flush" which is essentially the same thing. Your money. Keep it away from paint and plastic, it will do neither any good but will harm nothing in the A/C system and dries extremely fast.

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Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]