curious where you got this "general recommendation" because it didn't come from Optimum. We have never recommended the 2 bucket wash (in fact, Yvan LaCroix recommends against it). For a truly filthy car (mud encrusted) we suggest power washing first, but still an ONR wash. I've never had a car too dirty for ONR. Opti-Clean is a true waterless wash and can be used for spot cleaning or for the entire job...and many use it that way. Opti-Clean is a stronger cleaner than ONR and has it's place in a washing routine. For instance, sometimes during a rain storm I pull my car out to get it thoroughly wet, then use Opti-Clean as a safe drying aid to finish the job.