A couple tips:
For cleaning the nib of your ink pens (the kind you dip into the ink), soak the nib (I usually keep it in the holder/pen) in a little glass of Windex (glass cleaner) for about an hour or so. It should be nice and clean afterwards.
I usually just rinse my watercolor brushes in water. For my acrylic paint brushes, I usually swirl the bristles against the palm of my hand with some shampoo - the brush will feel fresh and clean and ready to take on the day.