With Ling Wu Chung's litany of injuries during SPW, no herb, acupuncture, or even most inner power arts of the period seemed able to help him until he used Shaolin's Yik Gun Ging.
Yik Gun Ging was indeed one of the all-time great inner power training manuals, but as we saw in DGSD, it wasn't the only or even necessarily the best one. Could Bak Ming Sun Gung, 9 Yum Jen Ging, or 9 Yeung Jen Ging have done the job as well?