...that is the question of traditional lather making.
There is a lot of talk about soaking: Should you do it? What brushes should you do it with? For how long? Hot, warm or cold water?
Personally I soak all my brushes, for about five to ten minutes, since then I have a consistent baseline to do a bit of contrast and compare. YMMV off course so if you are happy with just dunking yours in water before shaving, that is great as well.