I just use the three nail method. I place two nails in the inside upper corners, then I place one slightly below the bottom rail of the frame.
You place it over the top nails and bow the bottom rail over the lower nail. This bows it out and causes the sides two flex inward.
Wire the frame then when you remove from the lower nail the sides flex back out. It makes the wire very tight.
I had ordered a spring loaded wire holder from Kelleys, and these three nails came with it, and instructions. I think it works pretty good and simple to set up.
Just My two cents!