@IBob @nabijaczleweli thanks for the kind words and the recommendations. Let me remark on the soldering station that looks so high-tech and expensive: It probably does because it's also doing other things, has a hot air gun (actually broken in this instance), a power supply, a voltmeter … And can be had for around 100$. The lender speculated that it might mostly be used as a cheap "all you need to repair mobile phones" set for small shops specialized in that. As I didn't have to pay for lending it it and got it offered the minute I asked around for solder recommendations, it actually was my first, cheapest off-the-shelf option ;)

As for the cable stripping, well I guess my finger dexterity didn't grow quite as fast there as with the soldering … I somehow hardly ever found the sweet spot between "cutting the insulation" and "cutting what's insulated". Any tutorials on doing it properly with just the knife and the tumb would be greatly appreciated.