I haven't seen anything about it lately. Last I heard she was waiting for the samples from her supplier etc.
The prebuy is an opportunity to get the brushes at discounted prices. Lumiere puts up a (usually large) selection of brushes and you can buy them at wholesale prices. They did one last year around this time and I think you could get the whole set (which was a lot of brushes) for somewhere around $150, I think. They are Lumiere's regular synthetic brushes that they sell.
The trick to it is that you have to pay up front, and there is quite a wait to get the brushes. Once the order is placed, you have to wait for the brushes to get manufactured and shipped from overseas, which can take a while. Then when the brush order arrives, Lumiere has to pack and ship them all out to everyone. I am thinking last year it was at least 2-3 months. (I didn't order but I had friends who did.)
She also puts a lot of rules on it - for instance I don't think your order can be cancelled once you place it, and I don't think they tolerate it too well when people keep emailing and bugging them about "when are the brushes going to arrive" - etc.
