While my hair is quite long, it's also very fine, meaning that when I put my hair up in a bun, it doesn't support some styles of wrap- especially ones that have lots of layers going over the top of the head, or which want some bulk to create a sense of balance. I've experimented with layering scarves underneath, as in this style:
excellent tutorial for using a long scarf and tucking it underneath itself, although I haven't managed to make it work for me. I think I put my bun too low- but that's where it feels most comfortable and natural to me.
There are also commercial padded volumizers sold, like these (pictures courtesy of Pesky Settler), and available online as well.
And then, there's the DIY approach, for which I found an interesting tutorial here. It looks easy, and fairly cheap. When I get the materials together, I'm going to try this one myself. I'll let you know how it goes.
Do you bother with this? What are your techniques?