While some hardened technicians would insist on getting things done with a grandfather's kilowatt soldering iron, we suggest you to buy a modern soldering station with a hot air and temperature control. You don't need to be fancy, an entry level soldering station like YIHUA 882D, or JCD 8898, or YOUYUE 8586 would do, and it won't break the bank with its price tag of $50-70, more or less.
Throw in a silicone mat, a tube of no-clean flux, a can of solder paste, de-soldering copper wick, ceramic tweezers, nonwoven swabs and a bottle of isopropyl alcohol. Many of these things can be already included as perks with the soldering station.
Again, some would say that you need a multi-thousand dollar branded programmer but in real life the cheapest CH341A USB programmer works like a charm, especially after you fix the voltage bug.
Or you can buy an improved model, version 1.7 and higher, where that problem has already been fixed in design.
Add a SOP8 208mil to DIP8 socket adapter.
Also, it's a good idea to have a bunch of spare flash memory chips.
