Well, I don't have any experience with olive trees, but I don't own any jinning tools either. I used just a regular swiss army knife on my willow wood and it came out fine. Just go WITH the grain of the wood, or it'll be impossible. The rounded tip is particularly helpful if you want some sort of concavity, or the whole length of the blade itself can be used as a chisel if you want a large portion of the wood cracked off. Just be careful... right now I have a missing knife tip and a cut thumb as trophies for finishing my willow branch for a phoenix graft! Injuries and other damage is likely if not inevitable, but if you're careful you can keep these to a minimum. (Also make sure your blade is good and sharp. If it's not, and you don't have a grindstone, you can use the top of a crystal water glass.) Good luck!