Simplepolator allows you to interpolate compatible glyphs in the same font, without leaving FontLab nor interrupting your workflow.
Simply select two compatible glyphs and run the macro:
Five new glyphs will be automatically created, allowing you to choose the best variation.
Making it super-easy to apply the Gunnlaugur SE Briem's method on "How to make mistakes.
A quick video showing how to use it: