Large project build failures - how to manage third party assets

My project is at the point that it is too large for the cloud build system to handle. Majority of the time it just times out and cancels the build. My understanding is Unity doesn't do so well with large projects, and recommends splitting your game into asset bundles and code projects, which then get combined into one project. I understand the basic concept of how to do this, and have done it with some assets. However, I think a few third party assets are my worst culprits, and I'm not sure how I would go about moving them to a separate project. Any ideas?