So far, I haven't been able to cast two spells simultaneously. Dual casting was something I'd always intended to practice, but I just hadn't gotten around to it.
Until I deliberately put myself in a dangerous situation like this, I hadn't really felt the need for it. After all, learning to cast powerful spells more quickly seemed more important than dual casting.
Oh, by the way, the Railgun I fire with both hands isn't technically dual casting. It's just a technique where I use a line I've drawn to fire two Railguns in rapid succession.
Wind Search remains active for a while after it's cast, so that doesn't count as dual casting either, and the same goes for buff spells like Accel and Quick.
*(First, my goal should be to cast different spells with my right and left hands.)*
Eventually, I'd like to use time-space magic to speed up Judgment Ray or Gungnir, but I'll have to take things one step at a time.