I know this forum is full of people who swear by ONR as an alternative to hose washing. I also know that there are people, like the OP, who are hesitant about the whole idea. I also have some experience of my own with this product.
Like anything else, you need to balance your expectations with the amount of effort you are willing to spend.
This is especially true with ONR. The dirtier the car, the more time and care you will need to spend washing each section. The more there is to wash, the more patient and thorough you will have to be.
With the right amount of patience, knowledge, and care, just about anything is possible. The question is, is the extra effort worth the results? I could spit on a q-tip then use it to wash my car and still produce a clean, shiny, swirl free finish. However, it would take me a long time, and I would have to be very patient and careful.
so the answer is "Yes", ONR can be used on very dirty vehicles. But you must weight it against all alternatives. Is there a reason you can't do a regular wash? Is the $8.00 you pay to go through a touch-free car wash before using ONR worth the time it might save you?
For me, ONR is a "maintenance" product. I use it when I can't do a regular wash, but only if my paint is in good, clean, protected condition. THere is no doubt in my mind that a well LSP'd car is going to be easier to clean with ONR than a neglected finish.
I have used ONR on a really dirty car, but I clayed and polished right after so I was satisified when the ONR only got my car 90% clean.
