Radio Shack used to sell solder strips that were intended to be wrapped around a connection and melted with a lighter or a match. Part #64-010 IIRC.

https://www.amazon.com/Radio-Shack-Heat-Solder-64-010/product-reviews/B001TQMBA6

Just looked it up and scarily that was the right part #. I remember it well from working at the shack in the 90s because we NEVER sold any of it.

I was there the year they decided to charge $2.00 for the catalog.... there was almost a riot.

They really should have survived but they were so stupid in their management - they put sales of cell phones above profits. The parts were their bread and butter and they blew it.

Kapton tape is usually used to keep wires in place (like the thin jumper wires) after installation to keep them from flying free. You could use them in soldering to keep the wire in place although if you move 1 wire at a time on a rectifier board installation I don't think it's strictly needed there.

Why didn't you remove the whole transformer and do it on the bench?? So much easier!