People seem to be mixing up short field and soft field. These require two different techniques.
Soft field, you pop the a/c up into ground affect to accelerate, whereas with a short field you use standard techniques for take off, except you are rotating at a lower speed than normal and using a higher flap setting (generally...). Plus if needs be when lining up on the strip, if you need to, then shut down and push the machine back into the hedge as far as it'll go before commencing you take off run. With a soft field, one of the major issues is don't stop or you'll sink!
If you are half way competent, there is no problems with putting flap down just before rotation. That is a normal thing, especially if you operate from rocky or very short strips where you need every ounce of acceleration.
Pulling a couple of great big flaps through the air is never going to help your rate of acceleration!