Product review (2 stars): but it wasn't easy. I didn't have someone else to help so ...
The twistie tie solution worked for me, but it wasn't easy. I didn't have someone else to help so I came up with some additional methods.

Start the same, but put duct tape every 30 degrees to hold the wire in place. Be careful no to go too long along the wire, cause it can start to wrap around the wire.

Make sure to leave big loops in the twistie ties so your hands can fit in.

But most importantly, make sure to cross your hands, so that the right hand is pushing the left-side spring out, and the left hand is pushing the right-side out. You get a lot more force that way, easier to keep the wire close to rubber gasket. You can lean in a little towards machine to get the wire into the rubber gasket groove. Also, using this method the arc of the wire you create by expanding it, is more symmetrical. Thin gloves, like gardening gloves, are also helpful.

If you try and pull your hands apart, it's much harder, and the wire tends to get lopsided.