The other day I straightened a section of curved SS track. I took the ties off and did each rail individually. I have 18" of real mainline rail and laid the SS on it’s side on the plain steel rail with the arc up in the center. I used a steel hammer to beat the side of the foot. I didn’t worry about the rail head, it followed along right nice. I have polished faced steel hammers for metal work…
I’d suggest a mallet on a 2x4, the mallet, leather or plastic face, won’t dent and the wood will give some too.
One other thought, if you cut grooves to match the rail profile on the side of a big dowel (closet rod) you could run the rail over the edge like we do to remove wrinkles from paper. Many passes instead of few, to gently coax it into place… at the ends, use large channel locks to finish unbend.
To straighten metal with internal springiness, it helps to go past straight, into some reverse curvature, then allowing it to return to flat.
Other wise join a club and borrow/rent a bender.(http://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-wink.gif) Or join a different club and shoot for Abs of steel and return to your belly bends…(http://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-tongue-out.gif)
The ever helpful;
John