Best Practices for Finding Existing Contacts in Clay Before Importing

Is there a best practice way to look for existing / already enriched contacts in contact tables before doing find people in clay? We have a table that contains all of our contacts that we've had in CRM + through lookups in Clay. When I create an account list in Clay, I'm trying to find an easy way to first check to find all available contacts from our existing data before importing more. Is there an easy solve for this?