First off, let me say I have never done this before. However, there are a few things I know that would help:
1) forget about wood. Even if there is a way to get to 660 C by burning wood (which I doubt) it's going to be very tough.
2) try a microwave:
http://www.popsci.com/popsci/how20/15499aa138b84010vgnvcm1000004eecbccdrcrd.htmlContrary to popular opinion, you can put metal in microwaves. read this article, then maybe go to the link to david ried's website. Theodore Gray says he manages to bring silver up to 800C, which is more than enough for you.
3) If you want to use gas, try acetylene. It is cheap and easy to get by combining bangsite (Calcium Carbide) and water. You can by it online for very little. Plus, acetylene can go up to a couple thousand degrees (provided you get enough).
4) don't forget to remove the plastic lining on the inside of the cans, or you'll wind up with a big mess.