We discuss the simplification of non-deterministic multi-valued (MV) networks and their internal nodes using internal flexibilities. Given the network structure and its external specification, the flexibility at a node is derived as a non-deterministic MV relation. This flexibility is used to simplify the node representation and enhance the effect of Boolean resubstitution. We show that the flexibility derived is maximum. The proposed approach has been implemented and tested in MVSIS. Experimental results show that it performs well on a variety of MV and binary benchmarks.