connection contamination soldering insulated wires

30 AWG wire is my favourite choice for board-level connections such as bodge wires on PCBs or point-to-point wiring on a board when prototyping. Often it is silver-plated, and solders well. If it is oxidized then the silver is visibly blackened (happens in the UK weather!) then I cut the wire and re-strip it to reveal the fresh silver, but it needs top quality wire strippers (the "Stripmaster Lite" is excellent for 30 AWG).

For off-board wire-to-wire connections, for prototypes, if I have to use 30 AWG wire, then it is possible to crimp it to normal 0.1" pin sockets (even though the wire is so thin, it can crimp to such sockets), or it could be soldered directly to 0.1" male pin headers, by tinning the wire, and tinning the end of the pin header, and then tacking them together by just holding them against each other and re-heating.
Sometimes I'll use Blu-Tack to support one end to free up a hand. 

For a bit of strain relief, super-thin heat-shrink tubing can be used, or PolyDoh is great for covering up the joins and making the pin header into a nice connector. The PolyDoh is softened with a hot air tool and then pressed into place by hand (it's hot but doesn't burn).
For direct wire-to-wire connections without a connector, I use the same tinning and tacking method and cover with heatshrink. Usually 30 AWG wire is Teflon or Kynar coated, so the insulation is heat-resistant to the hot-air tool used for heatshrink (but it helps to have a very fine nozzle on the tool).

I use mostly 30 AWG solid core wire, so it's not recommended for off-board connections, but I do have some 30 AWG stranded wire (it costs a lot more than solid core, so I only use it when necessary; it's brilliant stuff but so pricey). The comments above regarding how to tin/tack it and using PolyDoh or heatshrink apply to solid and stranded, they both usually have similar heat-resistant outer insulation. and are usually silver-plated conductors. Most of the cheap 30 AWG wires from eBay/AliExpress etc are different; they come with softer, low-temperature, lower-quality insulation, and are probably not silver-plated either. The good 30 AWG wire is called "Kynar Wire" or "Tefzel wire". Worth buying a couple of different colors of it for on-board work, it's a great problem-solver on PCBs or proto-boards.

The photo below shows on-board connections using 30 AWG solid-core wire (blue arrows), and the off-board (orange arrow) is stranded (but not 30 AWG in this case because there was no need to use it).

Another example is in the photo below, where the white and yellow wires on the surface-mount protoboards are solid-core 30 AWG wire, but the off-board orange and green wires on the right side, are 30 AWG stranded. It could have optionally been crimped, although I didn't do that here.

30 AWG stranded crimped, for wire-to-wire connections or off-board-to-board connections is in the photo below:

30 AWG wire is my favourite choice for board-level connections such as bodge wires on PCBs or point-to-point wiring on a board when prototyping. Often it is silver-plated, and solders well. If it is oxidized then the silver is visibly blackened (happens in the UK weather!) then I cut the wire and re-strip it to reveal the fresh silver, but it needs top quality wire strippers (the "Stripmaster Lite" is excellent for 30 AWG).

For off-board wire-to-wire connections, for prototypes, if I have to use 30 AWG wire, then it is possible to crimp it to normal 0.1" pin sockets (even though the wire is so thin, it can crimp to such sockets), or it could be soldered directly to 0.1" male pin headers, by tinning the wire, and tinning the end of the pin header, and then tacking them together by just holding them against each other and re-heating.
Sometimes I'll use Blu-Tack to support one end to free up a hand. 

For a bit of strain relief, super-thin heat-shrink tubing can be used, or PolyDoh is great for covering up the joins and making the pin header into a nice connector. The PolyDoh is softened with a hot air tool and then pressed into place by hand (it's hot but doesn't burn).
For direct wire-to-wire connections without a connector, I use the same tinning and tacking method and cover with heatshrink. Usually 30 AWG wire is Teflon or Kynar coated, so the insulation is heat-resistant to the hot-air tool used for heatshrink (but it helps to have a very fine nozzle on the tool).

I use mostly 30 AWG solid core wire, so it's not recommended for off-board connections, but I do have some 30 AWG stranded wire (it costs a lot more than solid core, so I only use it when necessary; it's brilliant stuff but so pricey). The comments above regarding how to tin/tack it and using PolyDoh or heatshrink apply to solid and stranded, they both usually have similar heat-resistant outer insulation. and are usually silver-plated conductors. Most of the cheap 30 AWG wires from eBay/AliExpress etc are different; they come with softer, low-temperature, lower-quality insulation, and are probably not silver-plated either. The good 30 AWG wire is called "Kynar Wire" or "Tefzel wire". Worth buying a couple of different colors of it for on-board work, it's a great problem-solver on PCBs or proto-boards.

The photo below shows on-board connections using 30 AWG solid-core wire (blue arrows), and the off-board (orange arrow) is stranded (but not 30 AWG in this case because there was no need to use it).

Another example is in the photo below, where the white and yellow wires on the surface-mount protoboards are solid-core 30 AWG wire, but the off-board orange and green wires on the right side, are 30 AWG stranded. It could have optionally been crimped, although I didn't do that here.

30 AWG stranded crimped, for wire-to-wire connections or off-board-to-board connections is in the photo below: