Here's a great video -
http://www.youtube.com/watch?v=HTOGt4cRdJE
And another
http://www.youtube.com/watch?v=8kceRsPGtZ8
I bought the CurveMaster foot to do an apple core and a drunkard's path but there is such a learning curve to it and I have only played around with the apple core so far. I should have saved my money!