3Spin and 3Murphi are modified versions of the Spin model checker and the Murϕ verifier. Our modifications enhance the probabilistic algorithms and data structures for storing visited states, making them more effective and more usable for verifying huge transition systems. The tools also support a verification methodology designed to minimize time to finding errors, or to reaching desired certainty of error-freedom. This methodology calls for bitstate hashing, hash compaction, and integrated analyses of both to provide feedback and advice to the user. 3Spin and 3Murphi are the only tools to offer this support, and do so with the most powerful and flexible currently-available implementations of the underlying algorithms and data structures.