Mike,
I’d like to think I’m on the right lines, but being “right” is a responsibility...
I suspect I’d use my flat pliers, I think they’d fit between sleepers, and with a thumb firmly on the uphill bit, I’d apply a little clockwise twist between each sleeper to turn the end down a little. Gently at first, can do more on the second and third passes, definitely easier to get it right first time than to un-bend it later!
Real rail is heavy stuff, and it will sag due to its own weight. This is a case of physics not scaling well. It needs a bit of help!
same is true for model catenaries, the wire is too stiff for its weight which spoils the illusion unless you’re clever, careful or lucky, or all of the above, of course.
Atb
Simon