I have setup a system where I have taken the model first approach as it made more logical sense for me. Now when even I have some changes in the model currently what I do is
You can try Database Migration Power Pack - it allows creating change scripts instead of full database scripts but on behind it does the same procedure as you did by hand. The problem is that mentioned tool will not work with EF5.
Unfortunately EF migrations currently don't support models created through EDMX. Migrations support only code first approach at the moment.