I assume your heating method is just to warm up the cap seal to make it a more air tight fit? Why not just put the caps in some hot water to soften up the seal and then you don't have to mess with heating the bottles.
I've never tried using screw caps my self. The little hand cappers aren't horribly expensive and then make a nice tight seal. Of course you will have to go buy a case of beer (without screw caps) and drink them real quick
Or just rummage through the recycle bins of your neighbors.