The old ones with the tang work pretty good.
The new ones that crimp at the top, take a little more effort.
Make sure that it's tapped and clean.
Add a dab of oil to the threads.
Use a short bolt or spark plug (whatever you're dealing with) Lightly oiled and screwed into the Heli to run it down.
Once in place, you'll back the bolt/sparkplug out and use the set tool to crimp it in place.
My experience is with ones with a tang on them. I've had issues getting them started in the hole before. What I did was put it on the installation tool and wind it "up" the tool as tightly as I could. Don't know why, but the extra effort I took to wind it as tightly as possible up the shaft of the install tool is what seemed to make it go in for me. Once I got a turn of it in the hole there were no issues. Hope this helps.
Chamfer (sp?) the leading edge of the hole you are coiling - be sure to use a light oil or some sort of lubricant. Doesn't hurt to chase the threads a few times with the proper tap - sometimes the original cut isn't perfect.
the tanged inserts with the install tool are usually pretty straight forward. I usually start with one thread poking out of the tool and start installing from there.