Go here for some good insights:
very sensible comments made.
For example he shows the double 'garn sau' hands - that are broad apart onthe dummy but are close in application.
I have his video on wing chun 'Pure and Simple' and its very good indeed. Not many people talk about it, strangley. It's the only one that shows you how to use the hit fall wine - Dit da Jow - to condition your hands after sand bag use. He does this in a circular motion really rubbing hard into the area. I use this and believe it works - but don't know why - it could be just the rubbing itself ?