Planning is important. The correct time to attach the handrails to the Barclay tanks was when I could solder the knobs from inside. Instead, I left them thinking I could use a bit more heat and work from outside.
I could, but it needed a lot more heat. In the end I tinned anything that went through the brass body then smothered the lot with solder paint and Powerflow flux. With each handrail held in place with a screwdriver and the gas torch fired up to provide some quick heat.
The results are OK, if a little messy. Before cleaning the model up, it looked a real state with burnt and blackened flux over everything. A scrub with Shiny Sinks and then a bit of burnishing brought everything up to a shine again but it takes confidence, and experience, to know that's how things will turn out.