I think it is abit of a fine art to get a great B/J, definately don't get into it when a woman trys to give you head at 100mph.
To be honest not very many woman have actually made me cum by giving head, Though its good when you can stick your cock right down there throat and hold there nose, that's when a woman can give good head.
That has been very rare but one lady cums to mind and she still working. na not telling