Watch the pros from the Team O’Neil Rally School explain how you should be shifting while hooning. Don’t feel bad if you still get properly heel-and-toe, it isn’t easy, and as the video explains there are several ways of doing it. Practice makes perfect.
Shifting without a clutch is not so much difficult as it may cause damage to the transmission if not done right. I have tired it many times with mixed results and I always kept my foot over the clutch pedal just in case. Wyatt Knox, the guy in the video who I have met while hooning the Challenger GT, makes it look easy, perhaps too easy.