Silicone bronze mig brazing is not welding. It relies on capillary action not metal fusion. Typically you need a larger "root gap" to allow the filler material to flow around to the backside of the panel for strength. The process has less heat transfer and the main reason that oem's use it for hss and uhss in collision repair is to reduce the risk of further tempering the steel. Also has a less rigid joint when sectioning non structural panels. It works great for all repairs and is very strong when done properly. We have played around many times with metal coupons and then pulled them apart with the frame rack pulling tower (mig welding, spot welding, rivet bonding vs mig brazing etc). Also works well for filling in small holes if you damaged the repair panel with a stud puller or Lenco type dent machine. I use the pro-spot machine posted above and we have never had any known body filler failures. Like MrT mentioned the process is slightly different to traditional mig welding. Hold the gun further from the panel and do small tacks allowing to cool slightly between tacks. I'm an ICAR platinum steel structural technician.

https://www.youtube.com/watch?v=TQNpDQVc5wo