Personally, I find the critical is to use good wire (the type used in transformers), use a good soldering station with right kind of tip, and plan a way to conn

Personally, I find the critical is to use good wire (the type used in transformers), use a good soldering station with right kind of tip, and plan a way to connect to your wires without destroying entire setup. I solder the wires to a short piece of FFC tape ending with a connector. The tape and the connector are attached somewhere with apiece of double sided adhesive tape. The end of the tape with the wires is suspended in air nearby. I then individually solder the wires to the test points. I can then connect my test tools (scope / logic analyser / PSU / DMM) directly to FFC connector easily. If I need more than one tool, I would usually use one of my breakout boards with connectors that make it easy to connect multiple test tools at the same time (for example supply power AND connect the scope, or maybe inject external signal to the chip on the board). I would like to mention I don't do it frequently. This usually only happens when I am having fun with an existing device. My own devices usually have built in enough test points / test connectors to not require this kind of shenanigans. I would usually plan for one or more surface mount connectors that I will only solder if I need it for some reason.