Is the project proposal easy to read for an outsider, and is handing in a proposal easy?
For NGOs: You should develop a concise proposal that summarizes your idea and presents it in an appealing way. This could be, e.g., a one-page PDF or a visually attractive PPT. Before you hand in your proposal, make sure it can be understood by someone who is not familiar with your area of expertise. Don't use unexplained abbreviations, don't use academic language, don't be vague. If you can, make a short video. Make the festival understand how they will benefit from your project.
And please, don't ask for backstage passes. The festival will provide you with the necessary credentials if you do the project together.
For festivals: To simplify the proposal process, offer an application form that can be edited online. Include a "Save for later" button in your online application form, so it doesn't have to be finished in one sitting. Be transparent about what is going to be required from the NGO.