I've been using Greased Lightning Showroom Shine since it was first launched in the UK....
Like others I thought that rubbing dirt and grit particles into my paintwork was a definite no no as I reasoned that scratches would be inevitable...... however I was wrong! I did some research and found that as long as clean microfibre cloths were used and changed regularly ( washed as required and without using fabric softener) the grit and dirt particles were, as it were, "encapsulated" by the chemicals, and held harmless as a result.
Trying it first of all on a small and inconspicuous spot on my car I saw that there was no visible scratching even under low power magnification using a hand lens, so I progressed to an all over clean and still no scratches but a hard surface of (what is said to be) carnuba wax seemed to seal the surface paintwork.
I do the car twice a year with greased Lightning Showroom Shine and it does a great job, needing only intermediate hosing to leave a clean and shiny surface, as the dirt and bird dropping don't seem to be able to get much of a grip.
Impressed with this result I moved on to my caravan and throwing caution to the winds did an all over clean with the same stuff..... with excellent results and no scratching. Now I use it twice a year ( same as for the car) and again with just an intermediate light hosing and it keeps it looking great.
Usual disclaimers (I am just a happy customer, with no connection to them) but my car is now 19 years old and my caravan is 25 years old.... still no scratches ( apart from the one I caused by misjudging the width of my gateway!)
I hope this helps someone, and as always.
Regards to all and of course,
Happy Caravanning
paws