Separate hair into two or three sections (two is normal but extremely thick or long hair might need three)
Twist one section, pin it once or twice, drop. Twist and pin second section once or twice going the same way as section one. Pick up section one again and do another pin or two, drop and pick up section two, pin, drop etc. keep switching sections, twisting the section itself and winding it in a circle radiating from the center like a pinwheel. Eventually one section gets put together with the other as it gets down to the ends where it's thinner, twist both together,keep pinning in the circle and secure the little ends with regular bobby pins (it only takes one or two at that point). Wrap a hairnet around if needed, spray and done. It will look like a cinnamon roll when done, is very secure and the pins do not poke or fall out like regular hair pins can. The trick is in the pins, the way they are shaped... They go in "backwards": you hold the pin with the open end facing the hair piece and prongs curving downward. Now, as you insert it into the section of hair, you stand it on the open pron end and flip the prongs forward, pushing the pin in so the curve lays along the curve of the head. If you do this correctly, the flat closed end of the pin is nice and horizontal to the scalp and practically invisible, all you see is coils of hair. It's much harder to explain than to show, once you have seen it done correctly it's super easy, I promise!
Oh, and buns made this way stay pretty close to the head, they do not stick out like doorknobs the way some bun making devices buns do, so much easier to actually do gymnastics in. Gymmie dd prefers the two bun style because there's really nothing touching anything at all during any gymnastic move, but even a large bun done like this would not be a major bump for rolls etc.