More followers will make you more attractive to casting directors because you have a "built in" fan base.
This is especially helpful to filmmakers who do not have a large budget or a large following themselves. It is free advertising for them because when you promote the film on your social media the film is gaining a reach it would not have had without you.
During the submission process, you can mention your large following.
This is a great thing to be able to offer and helps out the film in the long run. Try to have at least 2,000 people actively following you before you start offering this service to industry professionals.
Learn how to gain followers easily. Facebook, Instagram and Twitter are constantly changing the way people find you, view you, and are related to your page. Constantly update yourself on what hashtags to use and the time of day to post that will get you the most views.
Incentivize people to follow you with free offers. Brainstorm five things you can offer to your fans. Look on other social media profiles of people who already do this and see what they offer.
How can you offer something similar but make it personalized?