We describe a method and prototype tool for purely declarative creation of "solvers" for a wide range of problems where instances are presented as strings. Examples include model finders for logics of moderate expressive power. The method exploits existing specification-based declarative problem-solving systems ("model-and-solve" systems), adding a front-end tool to declaratively map problem instances in arbitrary form into system-specific instance formats. We illustrate application of our prototype tool with examples including graph problems and nonclassical propositional logics.