I am about to have another go, I have let my fondant harden for a day (I think it might just crack though) and the ganache under it soften a little.
I will see how that works, anyone else have any other techniques they use?
I'm assuming you are using an imprint sheet? I use a diamond quilter to get the "puffy" look. Here's a link to it.
I do it right away, while the fondant is still soft, and has some give to it. I have a copper three diamond quilter/cutter from Jennifer Dontz. After you make the impression, go over the individual lines with a boning tool/skewer, with some pressure. Not so much that you cut thru, but it should poof the diamonds out.
I think the fondant needs to be soft. I did the cake in my avatar with the wilton embossing tool and a ribbon as a guide. Used stick pins to hold the ribbon so the lines were a consistent width apart. (Actually, to be honest I did that for the first 2 or 3 lines then it got tedious and I eye-balled it).
Yes, you have to work while the fondant is soft.