Gospel Trios

I have been arranging music for string trio (2 violins, cello) to play in church in July. For inspiration, I have been listening to acapella versions of gospel tunes on youtube. The question, for me, becomes "How do I use vocal techniques to create interesting string textures, and once I do, HOW do I notate such techniques?"

I am especially pleased with my recent version of "Come Thou Fount of Every Blessing" which has the accompaniment trying to imitate the "schoooom" of low voices. It certainly helps to explain it in person at rehearsal, rather than in print.