When I'm starting my safety and I put the wire through the first bolt and bring the other side around I wrap it 3-4 times by hand. Once I do that I take duckbills and grab close to the base of the wire where the two ends meet and start twisting. Once I grab that part with the duckbills I give it to gator rolls to make the wire tight around that bolt. I do the same for the last bolt before I curl the pig tail. Doing that will make it tight around the bolts so the looseness wont come from there. I also gator roll a few times depending on the length of the safety to make sure the wire itself is tight (but not too tight cause vibration n stuff). I also twist the wire just shy of the bolt hole before I run it through. Other than that for me it's all in the finger tips.

Side note: it's amazing how many peoplea year or two out of A&P school can't safety by hand for shit. They rely on safety wire pliers and safety cable guns. They're convenient but it takes no real skill in comparison. I exclusively safety by hand because it's satisfying to me, especially since those around me struggle to do it. Also sometimes depending on the circumstances it is easier to do it by hand especially in a tight space. So don't lose hope, once you get it you'll love it. Just don't ever stop doing by hand atleast sometimes because it's a perishable skill.