Ive not done that much pipe bending but that back tool on the second bender shown does keep the kinking down as it holds it in shape. however if i was planning on doing a nice shiny one id be tempted to buy in preformed bends and tig weld it all togetehr then have it polished as this looks minty mint far better than the kinked look lol
Have heard the fill with sand thing before but never seen it done so cant comment on that