Just thought some people might find this helpful, haha. I know the jaggy edges were driving me crazy.
Again, if strange black pixels keep showing up in your flele in places that should be white, maybe those areas are TOO white. So try toning them down a little.
I don't use the green background thing since my photoshop can save a transparent png with no background, and this seems to work alright with that. Presumably the pna file thing should still work with a green background, but heck I dunno.
Let me know if you have any questions, haha. I tried to write up a shimeji tutorial once but it got ridiculously long. You can read it here though - [link]
You can download Jockey here - [link]