Using Clay to Exclude Duplicate Companies and Contacts for Prospects

Hey. I want to start using Clay to find companies & new contacts for my own & my clients companies. However I'm concerned about paying for duplicate data... Since we already have lots of companies we got from Apollo & Instantly, want to find out is there a way to upload our existing Companies/Contacts to Clay & then exclude them when finding new prospects directly from Clay? If so, please let me know how.