I am a weldor..I have 25 years experience and 2 years of schooling. Those rods are a bit misleading to the average person. These are a tin based alloy that is NOT as strong as aluminum, and is not "welding" by definition. Welding is the joining of two "same" metals by "cohesion", where both the base metal and deposition metal are melted and flow together to become one. The video is showing the process of "adhesion". Where the base metal is not melted and the deposition metal is only "adhering" to the base metal. There is NO penetration in this process. This process falls under the category of soldering.
The break in your frame should NOT be repaired using that product. It has its uses, but anything structural or where safety is a issue should not be repaired with it. Like any pressure vessels, or things that if they broke, someone might get hurt.
Just take it to an experienced weldor. Do not clean it with anything like acid or brake cleaner, just leave it be. The weldor will know what to clean it with and should have that in his supplies. Some chemicals will get into the miro pores in the metal and give off some pretty bad fumes or contaminate the weld during the welding process. A guy brought me a dirtbike engine case to have tig welded. I cleaned it and fired up the TIG welder and and smelled a chlorine-like odor, strong enough to make my nose burn and eyes water. He told me he cleaned the part with brake cleaner. No matter how much I re-cleaned the part it would not go away.
An experienced TIG or MIG weldor will have no problem with that simple repair as long as you do not mess with it. He should also know how to reinforce it to help prevent another break. If you smear that solder all over the joint it will be a nightmare getting it ALL off to properly weld it.
Believe me, if all I needed was a propane torch and those rods, I would never have purchased a 2000 dollar TIG welder. And TIG welding would be obsolete.
If you have any questions, just ask. And good luck!