Can anybody suggest a good resource for understanding / selecting filler rods / fluxes? This would be, for now, general purpose for playing and learning but I'd like to be able to braze / solder mild steel, maybe stainless (as in sheet metal tanks), and maybe aluminum heavy gauge sheet. The choices seem bewildering and, unfortunately, the guys at the local welding shop seem far more oriented to arc welding and can't seem to explain what the "best" stuff to use is.

Thanks, BS