I converted my neighbour to wet shaving a while back and every so often he has a questions for me to answer, which on occasion, leads to a blog post. His most recent question was “how long he should be soaking my brush before using.”
The short answer is to soak it long enough to give yourself a nice, rich lather. The longer answer is dependant on what type of brush you are using. A boar hair brush is somewhat more coarse and its firmness makes the hairs a bit more brittle. Because of this I tend to soak my boar brushes for a couple of minutes. My badger brushes require less time, the soft hair absorbs the water faster than the boar hair. Of course if you soak for too long you can just give them a shake to release some of that water. It might be beneficial to fill your scuttle, bowl or sink with some water, toss your brush in, and let it soak while you prepare for your shave.
A brush that is properly soaked will help you produce a lather that has good body with plenty of protection, and help you from damaging you brush. The force from the lathering can damage the tips of the bristles if they are not properly softened. The dry brush will give you a thin lather that is frustrating to lather and creating a situation where you are more likely to nick or cut yourself.