I've ridden and raced many forms of bicycles... road, track, mtn bike. So I've had lot's of experience with road/mtn rash (and orthopedic surgeons). The best way I've found for softening up a scab in the mid to late stages of the healing process is to apply neosporin, or any other anitbiotic ointement, liberally to the scab. After about 20 minutes it will soften the scab enough to allow movement. A dressing of gauze (there are several brands on the market that will not stick to oozing wounds) will prevent your clothes from sticking to the softened scab.
Take care.