Reddit reviews Harris SSBF1 Stay Silv Brazing Flux, 1 lb. Jar, Black

you want the black flux

Go forward with brass to make your life easier. If you're still not getting solder to flow then it's the torch. A common favorite is the mini-torch, but you'll need the tank setup.

Heat the area evenly then go in for the flow by focusing a little more heat onto the soldered joints. Be mindful not to put too much on the wire prongs otherwise they'll melt before the solder does.

I ordered this: https://www.amazon.com/gp/product/B00EDMM4KU/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1

Would that work better?

I have not tried to apply more during the process.