There was no helping it, only pain would allow them to flourish. The members of Umbra had to suffer through some intense agony in order to eventually unlock the Body of Godliness.
The Avatar's precision helped immensely and was in fact the key factor behind this. He wasn't just hitting them and moving on, but striking their acupoints and meridians with enough force to jolt them open.
While it may sound tedious for acupoints and whatnot to be involved with Control, it was inescapable. After all, it had been the Oriental martial artists who had discovered the Body of Godliness since the ancient era, though they had called it 'cultivation', keeping it a secret from the world until the modern age.
It was only once the westerners had similarly unveiled their secret Void of Perfection that their ancestors had used for 'magic' and 'psychomancy' that a relationship had been discovered between both.