That web site is selling a water proofing cream to be applied to the outer face of the wall, supposed to stop rain getting through to the inner leaf and the CWI. My home is brick built, solid floors and had fibre CWI put in around 35 years ago. We live atop a hill, in what is often a quite windy location and have suffered no damp problems what so ever in that time. The cavities were checked and cleaned out around 40 years ago, plus having a chemical DPC added to the existing DPC.