It's been more than a decade since I did this, but I can give you the basics. The key is to start and end the clip at a point where the sound pattern temporarily hits zero (the horizontal axis). I used Audacity to do the editing. It had a feature that would find those crossings automatically, which made the process somewhat easier.
Will do, I might like to learn that and also be able to easily add rain tracks rather than always having to rely on some content creator to do the dirty work or be helpless when it hasn't been put out there yet :)
There are probably plenty of other audio editors that would do what you need, but Audacity has worked well for me. I've used it to loop tracks, to assemble tracks from multiple sources, and to break up audiobooks into chapters.
You think FruityLoops on mobile could do stuff like that? Don't mind paying and if I can do it self-contained on mobile, thats perfection and where I would play around with the most