If you're looking for an easy way to create an RSS feed of your Poshmark products, as far as I can tell, there's nothing out there to do it with easily. I was looking for a way perhaps using an api but found very little on the internet about it. There's no api, at least one that I can find, that can be used to do it so I decided to write a java application to do it myself. I did find some postings on various forums that indicated that Poshmark wants you to stay on their site and share within the app. They apparently have no interest in providing an api. If you have information about an api that disputes this please send me the info!
Why create an RSS Feed for Poshmark?
If you have an RSS feed, you can use services like Zapier, or If This Then That to automatically read your RSS feed periodically and post to other social media sites like Tumblr, Twitter, Blogger , and Pinterests' Bulk Create Pins (Edit Settings -> Bulk Create Pins). This helps you to promote your Poshmark items outside of the Poshmark site.
Getting the Poshmark data from the site.
I did find out by inspecting the HTML source that it's possible to get the URL's of the individual products from the user's main 'closet' page. Then on each product page, there were some json data structures in script tags but they didn't seem to appear on every page. In the head sections though, there is opengraph and twittercard data that can be used to extract what I need to create an RSS feed.
Poshmark to RSS feed application.
I decided to go the Java route because I've written quite a bit of code and was familiar with rome and Jsoup, the two main libraries I need to parse HTML and generate RSS.