Google Drive is Google's file sync app that lets you store all of your files online alongside your Google Docs documents, and keep them synced with all of your devices.
Give creators one revision task with feedback and the current file.
Your creator gets the reviewer's requested changes and current draft together, so they can start the next revision without chasing files.
Add approved briefs to asset reviews before reviewers decide.
Your reviewers see the brief beside the asset, with the brand decision they need to make clearly stated.