We have 4 members in a team working on a project that has one SQL dev database and our models are generated by Entity Framework using the methods outline in the MVC docs. Our problems arise upon trying to merge .edmx files and their related subfiles as it usually takes most of the day to ensure the models are generated correctly and it's just an utter hell.

I was thinking there has to be a better way to manage this but I can find any solutions for db first version control (code first is not an option as our databases always come from an existing source in another dept). We have tried to split up our .edmx files by feature but we often have multiple people working on the same features at once so it doesn't help too much.

Should we even be using the method outlined in the docs in the first place?
Should we use a seperate project entirely to handle the database?

Any help at all will be appreciated.