The solution is a best kept secret….LIQUID CHALK! I have a bottle which I take to class. Just ask if I forget to say. Or buy some from the web. Available from www.fitness-mad.com. See my relevant post.
Liquid chalk is fantastic anyway. I can honestly say that even when you don’t have issues with your mat being new and slippy, it still creates a marvellous feeling of stability and grounding in poses like Downward facing Dog.