As someone with a bit of knowledge in this industry, you won't get far with a good portion of producers. They are generally tech savvy enough to not fall for crap like spam. You need to offer them something they can use to help their brand and help them grow. Personally, I would offer publicity related services. A lot of producers lack any kind of merch, set up shop somewhere like amazon, hire a lawyer to write a contract, and offer to sell merch with their logos on it, paying them royalties for each sale. You have a way to get information from profiles, so scrape each producers following and email blast THEM with the merch products. If you want a more long term list of followers, set up download gates for the producers. Build a list of active users who follow them and sell them stuff.