[3.2 CAB]

I have a tip that is referred to as being a "rosebud tip" have also seen it called other flower names. The idea behind it is that it has a rather large output for the flame, about the size of a rosebud or a tulip. It is designed that way so you can heat the surrounding metal at a body seam, plus the center portion produce a flame hot enough to melt the lead solder into place. It is also used when you "plank" the newly sealed seam, the tip is used to heat the seam overall so you can then smooth it down with a plank. Are you using any type of flux? It the metal free of rust or other contaminants?
Advice: GO SLOW, USE THE PROPER FLUX, DO SMALL AREAS, TILL YOU GET YOUR TECHNIQUE DOWN AND THE GAS OUTPUTS HOW YOU NEED THEM TO BE ABLE TO LEAD SEAM FILL A CAR.
Good luck!! Tony.