Here's another vid, from Chapman cycles, showing process he uses to tin the tubes prior to building a fillet(a two pass method) by pulling a small amount of brass around/into the joint with heat. This is also helpful(for me) seeing the heat/color of the tubing relative to flowing the brass.
This is on a Vimeo vid by Steve Bilenky showing a bb he tinned, ready for building a fillet:
regards, Brian