Ive used the wolfgang leather cleaner and conditioner twice on my s550 so far and am satisfied with the results.
I spray a microfiber applicator pad with the leather cleaner ( I dont spray directly onto the leather itself) ,, I clean all the leather in the car and then with another clean microfiber applicator pad I apply the conditioner on all leather surfaces. The instructions on the bottles are fairly straight forward about how to use the product. I personally like to apply a little extra conditioner then I wipe off any excess with a mf towel after I let it sit for a while.
the wolfgang leather products definitely will not damage your leather and I personally think they provide good results. I havent used any of the other brands yet so unfortunetly cant provide you with a comparison.
Let me know if you have any other questions.