I see. The re-balling is quite straight forward but it does require some confidence and experience. Heat guns are not that expensive in the overall scheme of things but probably not something you buy for a single use only.
Solders a remarkable product, hard one minute - soft the next. It's getting a uniform heat across the chip thats the tricky bit that requires experience. Solder will attract solder and that's what they are relying on for re-balling. If the 'ball' is touching the original solder pad beneath it it will flow onto the pad when it melts - self centring when it does so. Don't go there if you are in any doubt - you will more than likely destroy the board.
I see the 45degree chip you are referring to and I sort off assume you are thinking of attaching a heat sink to the chip - fair enough. You don't have to glue on copper coins or coke tins as you can buy heat sinks from RS etc or Maplin etc. Maybe something like this?
ICK BGA 14x14x10 | Heatsink, BGA, 27.4K/W, 14 x 14 x 10mm, Adhesive Foil, Conductive Foil Mount | Fischer Elektronik
Am I barking up the right tree?