I am attempting brush embroidery for the first time tonight for a cake being donated to a silent auction. I think I have the main concept down, but if anyone would chime in with specific directions/tips/tricks, I would really appreciate it 
Thanks!
i love brush embrodery, my teacher in class said she would only do on someone's cake that was a close friend, we used the 6 pedal cutter just lightly press in buttercream, us a tip like 3 and outline, make the outline thick, I had bought some brushes at the dollar store that turned out to have a stiffer bristles than i need to paint, but i took one and cut into it with my scisors giving it a uneven edge, it works great, you can use the flavorings, alcohol, ect, the secret is keeping your brush wet, you take your brush put it on your piped line and pull towards the middle of the flower you won't get to the middle right away, and you may not want to, it's kind of like feathering until you like the look, i've even taken another color and feathered that in too when i'm done with the wet brush i kind of lightly tap down the outline. hope this helps.
I too love brush embroidery. Here's 2 videos (also love videos, easiest way for me to learn).
Buttercream on buttercream
www.youtube.com/watch?v=u6r8MYHYz00
Royal Icing on Fondant/Gumpaste
www.youtube.com/watch?v=FqbDTaauGO0
Thank you to Serious Cakes and Elaine MacGregor (I wonder where she got the beautiful design?)
wow i love the serious cake video's and the peach cake, i didn't know you could do it on fondant, wish i had some cakes to make, i think i'll make one tomorrow anyway, thanks for the video, so do you use the royal icing instead of the bc, and the second one she did on the plaque do you just put the plaque on the cake or was that an example
OMG - I LOVE brush embroidery. I do it on BC as well as fondant AND I do it WITH BC or royal. I did BC on my flip flop cake in my pix which was covered in BC too. Same concept for either BC or fondant. The key is "not too much water" when pulling the icing. 
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