I've tried Prepolator and it works but I frequently found difficult to select certain contours or to arrange orders when there are several contours involved (for example in an AE with many overlapping contours). In such cases it is a pain and I tried to solve the problems natively in FontLab but the rutine of using scripts for im/exporting UFO is also a pain and rather slow. I recently bought Glyphs to see if I can find a better way to make masters compatible dealing directly with UFO files (my main interpolation software is Superpolator). So, I am curious about what is the workflow / tools you use for dealing with interpolation masters...
(It's on my list of things to possibly change.)
There are also FL scripts to import/export:
1) only the selected glyphs in the current font, or
2) the selected glyphs in all open fonts
So if you tweak a particular glyph, you can only export that one, and it only takes a fraction of a second.
+ with the same contour order