Looking for a service like Buffer but for P2P e-commerce sites

Hi, I'm selling tons of products on pages like craiglist, ebay, offer up, amazon... And it's a very very big waste of time and painful to create and maintain the product ad in every page. I'm looking for a service that works like buffer.com (which schedules posts on social media) but for P2P webpages like those ones.

Do you know something like that? If, not, I'm a programmer too – do you want me to build something like that? hahaha