as for special tools, sometimes there just isn't the right one, from my welding classes, one of them was an art class and i had to find ways to bend all different thicknesses of sheet and solid stock to look and fit just how i wanted....i'd like to think i pulled it off quite well....will have to upload a pic of the work i did, got to put it in the college art show...anyways

for bending corners, you could use some pipe, preferably something bolted to the ground or something very very sturdy, being able to clamp it would be great, for those straight bends i used a vice with thick steel plates to extend it's "clamping" length, and then a steel pipe of the diameter of the bend i wanted to make laying on top, slow and steady preasure got me the bends i wanted even without heat

hope that helps a little, sorry if i started to drone