error 0102 GPU Reflow Question

I am new to repairing xboxs and have been doing pretty well but when it comes to heating up a mother board, I have been having some issues. I tried following the directions on here for the reflow but messed something up. I did some more research and found conflicting information about how to do it. I have the air gun that Ifix sells and there tool kit (thanks).

What is the best technique for the hot air gun? Some people say not to heat up the whole area Ifixit recommends( saying it to risky and will cause more problems).

I have Error 0102 which means I need to 1) X-Clamp replacement which I did, 2) Reflow GPU and RAM, already failed once but have another xbox which is untouched with the same problem.

I am looking for some tips and tricks on the best way to reflow an xbox 360? Do I need Kester?

Also found a amazing website for repairing xboxs, has tons of great information.

http://xbox-experts.com