I've read about using willow water to encourage plants to root and wondered if anyone has tried this.
Also the fungus gnat are consisted a nuisance in orchid growing but don't really hurt anything.  Are they that much of a problem in figs?

Gnat larvae are the issue. They can burrow into the cutting creating little pinholes that promote rot; also feast on young roots. Can really wreak havoc on cuttings. At the advice of many, I bought some Gnatrol powder (cheap on Amazon). I add about a cap or two to each gallon of water and bottom water my plants. I haven't had a huge gnat problem, but did it just to be safe. Not sure if its working, but haven't seen hardly a single gnat. So cheap, there's really nothing to lose by adding it to your regimen. 

I actually sell quite a large amount of willow cuttings on eBay for that very reason. I don't think they are rooting figs though.

Good, bad, ugly, evil, gnat ...

Interesting since I have never worried about the gnats with the orchid seedling.  When I rooted the cuttings I did nothing to protect them and most rooted fine.  I think there were about 4 different types.  I lost them during the moving process to lack of watering.

Willow tea, aspirin, humic acid are all related in content  with IBA being the constant if I remember right, they all seem to work well.  I have used all three and get a fuller foliage and it seems to root quicker when pre-soaked in the elixir.  I usually use humic acid and I soak the cuttings for 24 hrs.  I have kept notes on this and the humic acid is the best.  Nothing scientific maybe imagination.  I also use a humic acid elixir for liquid fertilizer.

is there any chemical difference between aspirin and willow bark?

i always thot them identical.