Aloha Toybrota

To be honest , we all have done it from time to time.  It happens.

I think Ur friend is pointing U in the right direction.  U might just have one of the pivot points sticking or caught a shoe in the drum.  U might start by backing up & tapping the brakes as U do , U could lucking ? ?

Cralw under Ur truck & check out the cable , the adjustment arm then look at the axle.  The pivot point on a top of the diff , follow the cable down both sides to the backing plate & check the levers there too. 

U're just looking to see if the cable is still pulled tight or a wheel cylinder is forcing the pistons out against the shoes.

Hopefully it's that simple.    Best of luck to U.

        😎🌴