I learned the song from the Stanley Brothers, and I perform it regularly with my partner in sort of a bluegrass-style arrangement. Besides the verse you know there's these, might be more somewhere:

Go yonder Moses and smite that rock
Smite that rock, smite that rock
Go yonder Moses and smite that rock
For I am the Lord thy God

Stand here Moses watch salvation work
Salvation work, watch Salvation work
Stand here Moses watch salvation work
For I am the Lord thy God

Good luck, Chet W.