If I was going to give only one point of advice for bending thin walled tubing, no matter what bender, whether homemade or mass produced, the tube must be full supported around its circumference at the point of tangency. This makes or rather wrinkles any good, bad or homemade tube bender's ability to bend thin walled tubing.

One comment would be to understand what is going on with the tube as you bend it. Simply put, when you deform or bend something, material needs to go somewhere. If the tube is to stay round in it's entirety the length of the bend, you are effectively moving material around. The material on the inside of the bend is thickening while the material to the outside of the bend is thinning. This is a good reason why fully supporting the tube at it's point of tangency is paramount.

Bending matched pairs of any bend takes practice and understanding how the material "reacts" to your applied force. There is a definite "feel" and this only comes with practice with the material. It also takes practice when compensating for spring back. Working from a full scale drawing really helps. In terms of methodology, having a way to accurately keep the tubes in phase is helpful as well as a series of stops that allows you to "know" where a bend should start / stop. Being able to measure/read the angle of the bend is another helpful aid.

I cannot comment on heating tubes to bend them as I have only ever bent them cold.

Never underestimate the amount of force you're going to need to bend thin walled tubes. The base you mount your bender to must be robust and have the ability to resist rotation. If you build your own, this is another good reason to over build it. Mechanical advantage in the form of a long lever arm is what I like to refer to as my "persuader". Tubes don't want to be bent as they will resist you throughout the process. They need gentle persuasion.

Hope that helps.