Chris Chewter

Do you have a Kadee plastic pointy stick (uncoupler).

It has a sharp end with a small plastic prong that I would imagine is perfect for holding a spring whilst you wrestle it into the cavity.

Or use black tack.

You still need to hold the spring correctly, otherwise it doesn't work!

Don't put the tool into the spring centre, but towards one end, 3/4 of the way.

Then put the longer section into the body end and then the coupler head end. Much easier, doesn't work 100% of the time, but does significantly reduce the losses!