If it can be sprayed on rocker without removing any trim, it will save time and I do not need to prepare clips - some old clips may be loose -.
As in this picture, Waxoyl spray is like a fog. So perhaps it can be sprayed on the whole rocker panel just by opening the jack hole cap. The inner end of jack hole is open - there is a gap between the inner end of the hole (cylinder) and the inner vertical wall -.
By the way, John Robison at Robison Service replied "We can remove the rockers if you want". He did not say "it has to be removed." But it was in his quick email reply, and he did not see my car.
But there is a chance that it can be sprayed without removing the plastic trim.
By the way, according to MB service CD, all the lower plastic trims above the rocker must be removed before removing the trim on rocker. Not a five minutes job.