I used bendy rollers (jumbo curlers) available on www.JumboCurlers.com as well as #60 and #18 clip-in hair extensions from www.GlamTimeHair.com .
Check out this video to learn how to use foam/sponge hair rollers to volumize thin, flat, straight hair without heat or teasing. It's not only a quick and easy technique to create beautiful curls, but it is also a very healthy technique as you can leave your hair to dry naturally overnight while sleeping on these soft and comfy curlers. This way you don't need to apply any heat to your hair preventing eventual damage! Of course, you could blow dry your hair too - it will take you 15 to 20 minutes.
These natural looking curls adapt to most of my curly updo haistyles for long and medium length hair, for example curly updo from www.youtube.com/watch