I used to draw out my bends,sometimes number them too.I've spent ,many winters bending up metal stock,counter flashings,drip,gravel stop,etc..and the practice paid off.
It's harder for me to teach someone to install it right than to bend.I like to wrap everything before the siding.bend all my flashings with a nailing fin.can't stand to see metal face nailed.it's easy and cheap.all metal should look sealed before the caulk too.I've seen some windows with 1/2 gap in the corners,with caulk all over it.
I've done a few round ones.I used some metal shop speciality tools to get the metal to curve.and it was coated galv and not aluminum coil.guess it depends on what your doing it for and what they expect.
did a quick search and found this.
http://www.toolsplus1.com/shrstretch.htm
looks like it but the ones I used were much older.