to Mathew's approach. I did a crash course in star collimation out of necessity and have developed a similar approach.
I collimate at night as well. The doughnut method works great to get started using a 20 or even 15mm EP. I then quickly move onto 9mm and 6mm EP's, adjusting as I go. Use very fine adjustments, you can get skewed off to one side very quickly if you over adjust and try to compensate (learned the hard way
)
I currently have managed to get mine down to a 4mm EP and collimated to a Mag4-5 star. The Airy disk is very stunning when the seeing is good.
Oh, and I have not "cleaned" my corrector plate since purchasing the scope (4-5 months or so now), I simply wave a eye glass cleaning cloth around a few times to blow away any dust or bits that might have settled before I put the cover on.