Leave the orginal Ground Braid in place. Then go back and forth. You should have a good idea on the proper track it should follow. You dont need to make a template in my opionion.

I reused Ground Braid on my Cyclone restore. Both Playfiled and Cabinent. Ask me if i would do it again..."NO".

I cant stress strong enough. Buy the new ground braid, and the correct staples and stapler. It's just not that expensive. I promise your work will go smoother, faster, and less problematic.

I am facing this at some point, also with a Cyclone playfield swap. What stapler and staples would you recommend?

I bought mine here...
http://www.pinrestore.com/Tools.html

Along with the cooper staples. Exact match to the original Williams.

Use new lamp sockets and leave the old ones along with the common braid in place. By the time you have the new sockets in place on the new playfield, and using the existing as reference, it will be a breeze.

Here is a less expensive option for the staples.

http://www.harborfreight.com/3-in-1-stapler-brad-pin-nailer-93749.html

It does not have the long nose but if you are doing the braid first it is not an issue.

Here is a less expensive option for the lamp sockets if you are replacing them too.

http://www.allelectronics.com/make-a-store/item/ls-9/mini-bayonet-base-lamp-socket/1.html

I've moved the ground braid with all parts attached when doing a swap. It took a little bit to get the right technique for removing the staples. The braid will break in a couple of places, but easy enough to repair that after the move.

Before I did the move, I took a pencil to trace where the braid had been to use for reference, but once you put the sockets back into their spots, the braid pretty just goes tow here it should.

I just unscrew everything and slide it over to the new playfield so everything is pretty much in the right place. I do this by using a few pieces of heavy cardboard (flat fedex boxes) that I slide under the parts, and then slide those all at the same time to get it on the new playfield, and then just pull the cardboard out keeping the parts from sliding with it. By using three or four of these pieces of cardboard, you can keep everything pretty much in place.

Harbor Freight does sell an 'upholstery' style staple gun which is what you want, since you don't have to be flush with the playfield. (I assume you have an air compressor, and if you don't you can buy a small one, they come in quite handy for lots of things).

This is not the model I have, but looks similar . . .

http://www.harborfreight.com/20-gauge-wide-crown-stapler-68029.html

or this might work, hard to tell the depth of the tip . . .

http://www.harborfreight.com/18-Gauge-2-in-1-Air-NailerStapler-68019.html