Dross is considered an impurity which needs to be removed in the smelting process before a vessel of good form can be realized. Many times, we maintain some element which keeps us from being pure and whole. This "dross" is something that when removed, will help us to reflect more purely the Creator within us and be a more wholesome vessel.
While most of us don't have exposure to this process of metal-working, what we can imagine is a pool of water filled with particles that might keep us from entering it. As you are trying to reach a higher level of cleanliness, whether physically, mentally or soul-wise, practice this simple meditation:
(Note: While most people associate meditation with Eastern faiths and not Judaism, this is a popular misconception. Meditation is not foreign to Judaism. In the days of the Temple and before, meditation was a known component and practiced. Meditation should be approached with an "open mind." For more information on meditative techniques, see the source Jewish Meditation by Aryeh Kaplan.)
Find a comfortable seat in a quiet place. First, take a few deep breaths. Deep breathing brings oxygen to your brain and helps clear the mind. Close your eyes. Continue breathing until you feel relaxed.
Imagine you are sitting beside a small reflecting pool outside in a garden. As you gaze at the pool, you notice that there are leaves and other tree particulates floating in the pool. Near you lies a net which can gently take away these elements floating on the surface.
Taking the net, contemplate an area of your life which you wish to purify. Focusing on the reflecting pool and the net, lower the net slowly and take out this impurity from the pool. Do this slowly and with intention; if you strike the water too hard with the net, you will make waves and cause the particles to float further from your reach.
Concentrate on those elements that you wish to remove from your life - remove them one by one from the pool. Try and hear the sound of the water, gently being dipped into, and the pool becoming clearer and clearer of impurities. If you don't remove them all in one sitting, just remove the ones that seem to be the most glaring.
What this exercise will have achieved for you is mental focus, lowering of your blood pressure, controlled imagery, and a moment to illuminate the obvious pollutants to your soul-life. By removing the impurities, you will be a better reflecting pool of the Divine - pure and uncluttered.