I wondered why I had so much trouble soldering. I went into Repco to get some decent size solder and some flux and the guy didn’t know what flux was. He said people don’t solder things any more.
Here is some good old 2% flux cored solder. Perfect for XT60 , XT90, Deans, JST or whatever fitting.
With this stuff you just tin your iron with it and go. No more feeding and feeding in skinny little wire. Save heaps of time and heaps of heat so helps in not overheating your plugs and wires.
Its not cheap because its the real deal.