Any song works. To make a stepfile, you need StepMania, and judging by how well you know SM and how well you can step, depends. The fastest I've made a chart is... probably 2-3 hours or so? And then there's one's where I've gone and tweaked stuff over a course of a few days.
As for getting it in FFR, you need to submit it and wait for the batch to be closed. They usually close it at around 100 files or so. then the judges will give ratings and if you get a high enough rating, your song is queued for in-game. This whole process takes anywhere from weeks to months.
Also, I have submitted "Thrash the Plank" by SnappleMan so maybe we'll get another OCR gem in game soon.