Soap is probably not good for them, if they were to ingest it it would cause some problems... to answer the "how often" question: i see birds every 2 months (sometimes more frequently but this is the recommended norm) and the quicks will actually grow shorter by grooming more often. If you were to wait 6 months to a year(yes, some people really do this) the quick will grow with the nail, so when the nail is extremely long, the quick will be as well. not something to worry about if you are properly trimming the nails every month or two. The rate of cutting depends on the season and bird as well too, every one grows at a different rate.
BTW i would never cut a green cheeks nails too short, only remove what is too dangerous(if it is getting curly) and file to a small extent to remove sharp ends. giantmoa what you are doing is probably perfect. I always leave a little "grit" feel for the little guys so they can hang on!
also leaving a bleeding toe alone is probably a bad idea, doing something to help stop the bleeding is better than nothing! i have never heard of a bird bleeding to death, but birds are small and do not have as much blood as we think they do. it's best to save them from bleeding as quick as possible. qwik stop is my first choice, then corn starch, then flour. apply your powder, add pressure and wait 30 seconds. Keep a close watch on the toe for up to 10 minutes, then a loose watch for up to 1 day.