Not totally sure about brass, I use copper, but hard silver will do the trick.
You'll need Flux too.
Brazing with hard silver takes a little practice, I recommend that you try a few practice joints first.
Good luck, have fun!
I would strongly advise against using that solder as the flow temperature (1350 degrees f) is very high. There is a good chance that it will harm the blade. Rather, use a low temp solder like 'Tix' or 'Stay-bright' which flow at about 400 degrees. In addition, you will need a torch setup capable of reaching 1350 and getting dissimilar metals to the same heat at the same time Takes alot of experience.
Yes. I would use 'Tix". you can get it from www.riogrande.com. Make sure you get the right flux to use with it. Additionally when it comes soldering anything---clenliness is next to godlyness. Clean with denatured alchol. Make sure the parts fit together perfectly. If you are around Cincinnati Oh you can come by and I'll show you how to solder.
smithy - you are thinking of soldering like a guard, in which case you are just right.
with a habaki, you solder it off of the blade and then slide it over the tang. The solder is just to close the bottom of the habaki. It will be subject to a lot of stress, and needs ez flow silver solder (it is high temp, but the lowest of the high temps so that you won't crumble your brass). You can also get dynaflow brazing rods and braze it shut. Either work. Get white paste flux for high temp soldering and brazing.
There is a tutorial on Jesus Hernandez's website that will walk you through it. I make these often for Chinese swords, they are called tunkou. I even have to make them double-eged, which means soldering both sides together instead of one. I definitely use braze for that.