I find it useful to right-click on an interface, and click "Implement Interface." This will create any missing interface members in a new region. However, if your interface has recently changed (ie some of the members already exist, some do not) the members will not be placed together in the same region.
Is there an easy way to collect all the members of a given interface in the same #region?
For bonus points, is it possible to have the members moved so they appear in the same order as in the interface declaration?