If you are using git-flow, this should probably be done in a hotfix branch, so that when you are done, finishing your hotfix merges directly to master and develop. Without a hotfix you would have to manually merge master back into develop.

It sounds like git-flow removes some hassle, can anyone answer the question about adding git-flow to an existing repo?

Running `git flow init` in an existing repository will ask you which branches you want to use as master- and development branches. So, yes. :)