As a groomer who teaches about canine skin and coat and methods that support the lifetime integrity of both, I have always been leery of working tools on wet, matted or packed coat.
For a long time I have tried different methods of unpacking coats in the tub to make the HV drying process faster and the mechanical workload of brushing as little as possible.
Aside from applying conditioner and using the HV dryer to blow out packed hair, they were very little tool methods that incorporated the act of combing or brushing clean, wet hair, that I knew weren’t somehow damaging hair coat for the long haul.
I found that this method proves to not break coat, not irritate skin, and not be physically tiresome or time consuming.
This method happens to use a dull undercoat rake and a protein conditioning treatment as a hydrating mask that provides a great amount of slip to help the packed hair out of the coat.
I’m also attaching a shorter video in the comments that utilizes a similar technique using only pure water with low pressure and high volume.
It works wonders, and keeps the mess in the tub and the groom time efficient.
Most of all it doesn’t stretch and break coat and set it up for matting right back up again!
** This is NOT a dematting method nor for use on curly coats. It is for unpacking double coats and undercoat.**
And a pure water rinse method as well.