The easiest thing to do on exhaust is buy prebuilt mandrel bends. You can get them from Jegs, Summit, even JC Whitney.
I just received this tubing bender yesterday: http://www.speedwaymotors.com/p/6614,,_3rd-Generation-Speedway-Hydraulic-Round-Tubing-Bender.html?itemNo=TUBING+BENDER
Looks good but I haven't tried it yet, tubing should be arriving in the next few days.