Today was my first experience with Sonus Block as well. It has been sitting in the bottom of the box so to say for quite some time. I have been hesitant to use it as many others on the forum have complained about marring issues. Well, I set out to detail my father's Envoy XUV as a b-day gift. When I got home there was a ton of tar everywhere. All the usual places plus in all 4 door jams, on the roof, and all over the tailgate. I just happened to bring Sonus grey along with the usual green out of sheer luck. I'd probably still be out there if I used the green. The vehicle is a light silver metalic so I though I'd give it a go with the grey. For a little extra insurance, I mixed up some double strength ONR clay lube. Any marring left behind was removd with easy by poli-seal. I then topped with Blackfire APP for a slick, glossy finish.
Maybe I'm lucky or the stars just aligned for me. Stuff works great and defintily had the bite required for all the contamination present. Also, as a side note I found it far easier to work with than the Blackfire clay sold by properautocare. The Sonus grey is far easier to knead in comparison.