You can wash the quills in warm, soapy water, but you might want to wait until you've sorted and trimmed them first.
Some people just use a towel.
Then I begin to sort the quills based on their circumference. When I have enough for my project, plus a few extra, I stop. Stay away from the curved quills or the ones that have already been bent and kinked. I usually keep handy a bugle bead of the right circumference for the seed beads I'll be working with. This builds a strong base row.