How many members of the cast of Glee do their own singing?

On the series Glee how many of them actually do their own singing? About the only three that don’t appear to be lip syncing are Rachelle, Kirt, and Mercedes. And when Gwyneth Paltrow sang in the Substitute (being a product of Hollywood nepotism) did she do her own singing? And do you believe Glee the series is making glee clubs in schools and out more hip and cool?