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You can get water spots very quickly if that's what you're talking about.

Here is a relevant thread with lots of info:

Rinse, wipe or dunk? How to clean lather from the blade while shaving

Here is a link to one of Mantic59's videos on lathering:

The Art of Lathering


Personally, I swirl my brush on glycerin soap (cheap stuff) for just 4 or 5 seconds before lathering with Proraso...