How do you tension steel wire?

So I'm installing wire between two 4x4 wooden posts. I've done two but it seems to take forever, so I know there's a more efficient way.

Here's what I'm doing:

1. The wire's plastic-coated, so I remove about 5" of plastic coating and crimp one side (where the eye screw is).
2. I take the reel and go to the other post, with the turnbuckle.
3. I reach the other post and I pull the wire (without bending it) to know the distance from the eye screw to the turnbuckle, say 30ft for example.

I add about 7" (for the crimp) and cut the wire. Then I remove the plastic and put the wire through the crimp.

The difficult part is pulling the wire so it's as tight as possible, holding the crimp so that it doesn't move, and then trying to use the very heavy and very uncomfortable swaging tool.

At the end, I'm able to crimp the sleeve, but the wire's sagging. The turnbuckle tightens it a bit, but it could be tighter.

Is there an easier way? I was considering buying a tool that I can use to pull the wire, but I don't know.

Put the crimps sleeves in place with the screw eyes apart the distance of the poles minus 1 inch (1/2" for each side) and fasten it all together. Set one eyebolt into the post all the way in except the 1/2". Important, count the full turns it took top get the eyebolt in that far. With the other eyebolt in place on the cable, twist the eyebolt counterclockwise the amount of turns it took to get the other eyebolt in, then add a few more turns if possible. This will insure the cable has the best chance to be tight when you are done. (This is what the 1/2" extra on each end and the extra reverse turns are about) It may take a bit of effort or extra help to control the reversed cable, but start it in the pre-drilled hole and turn the screw in. That should get you tight, at least as much as 2 wood posts will allow.

I did this with concrete threaded inserts on both sides of a concrete wall and 1/8" stainless steel cable between them, and they got bowstring tight. I installed about 14 of them in a room for hanging things from.