Policy briefs don't acually influence anyone involved in policy cause they have opinions already

Not everybody involved in policy has his opinions already formed. When a new issue comes up, politicians have to form an opinion about it and don't have to have a premade opinion.

The point of lobbying often isn't to convince a politician but to provide the politician with arguments to back up a position that he already holds. It's also to help with written the actual law. As far as I know the Global Priorities Project succeeded into getting an amendment that they wrote in actual law.