I cleaned it using the following process:
1) First, I used a sponge to wash it with some dishwashing liquid and warm water. This didn't do much because it was as dirty as a cymbal can get.
2) Then I let it soak in one part ammonia/three parts water for 30 minutes. After that I scrubbed it with a nylon-bristled scrub brush. This actually pulled a lot of dirt and gunk out of the grooves.
3) Then I sponged on Wright's Copper Cream >http://www.walmart.com/ip/Wright-s-Copper-Cream-8-oz/17352461 (I got it at Walmart for $6.) I just spent about 5 minutes rubbing it in on the top and bottom and then I started sponging warm water into the mixture.
4) Then I rinsed the rest of the cream off with warm water. I gave it one last sponge clean with dishwashing liquid and warm water to get the cream off. And then rinsed it really well with water and dried it.
Aside from the soak time in the diluted ammonia, the whole process took about 20 minutes, and the total cost for the ammonia and Wright's Copper Cream was just over $7.
I got all of this information from George Lawrence's excellent article, "The Dos and Don'ts of Cleaning and Polishing Cymbals" that I found at this link http://www.finishing.com/214/83.shtml It's about halfway down the page at that link.
Hope that info helps someone else,
E