How do I apply sugar crystals over the entire cake and sides without messing up the buttercream??? Where can I get sugar crystals, but a medium size not the really small sanding sugar.
I got some sugar crystals about the size of small gravel at my local cake shop. I think they came from CK. The cake I completely covered in sugar was fondant, and the sugar I used was Wilton's sanding sugar, so it's not quite apples-to-apples, but I painted on a thinned layer of piping gel and then applied the sugar the same way I would side-crumb a cake.
If I were to do this in buttercream, I'd do it as soon as I got the buttercream on the cake while it was still fresh and not crusted.
I know that's not much help but maybe this will also give you a bump so someone else can help you.