I am a natural light photographer that is venturing into studio/backdrop portraits at the request of some of my clients.
I have a portable studio for my needs with a white muslin backdrop.
I am using one (maybe two) Speedlite 580 EX flashes with shoot through umbrellas as lighting.
In my practice shots, I cannot seem to get a nice "blown out" white background without dulling my subjects (decreased contrast/lighter exposure on their face and clothes).
I am not a fan of seeing the muslin draped or crinkled in the background... although I know that's definitely a style... I will probably iron it but I can never get it perfectly flat and plus I need to transport it so it will get some wrinkles.
Also, what can I do to avoid any shadows against the backdrop itself (shadows created by the subject). I do have them placed slightly away from the backdrop but kids sometimes move around. Also if I am doing little children, I don't think having a small backlight would be practical (not that I have one... )