Yeast Washing the Wyeast way
This is my yeast trub in a 1-gallon jar. As you can see it was just about a half gallon's worth. I had boiled and cooled a little bit of water that I dumped into the primary to help allow the yeast to separate from the rest of the trub.
After 20 minutes (in this case) the yeast separates from the rest. The yeast is what remains floating on top in the water.
At left is what I poured off the top, the suspended yeast and water. I also had added some of the boiled and cooled water to the Mason jar before I poured the yeast into it. At right is the trub I left behind.
This is the yeast starting to settle in the Mason jar after 1 hour. I intended to wash it again but...
After 2 hours it looked like this. I thought this was adequately washed. It is pretty much all yeast left. Wyeast suggest washing it twice but that can be up to you.
HERE is a quick and dirty way to reuse yeast on brew day.