portapower with pullback ram....
'bar clamps' might not have enough strength ??
use 3/4" threaded rod to make your own 'bar clamp' ?
yes, pix would help...
generally you start at the worst bend,then add 2 clamps +-1/2 way away,then 4 inbetween them...
a slow process but the idea is to gently straighten the steel
it's a real 'hands on' event though.....