The interesting thing is, I've never really shown her how to do it ... she's just sort of seen it done ... and decided to try it herself. She used advance-and-retreat technique, with which she had great success. As you can see, Lace is quite content with matters as they are.
How, you may well ask, did any of us ever get anything done in this world ... before we had such clever teenagers to show us the way forward ... ???