Update:

I attempted to play around with the PCB from an old cable modem. Just touching the joints with the iron and trying to put more solder on them. I learned a few things:

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1. I'm really OCD about the lead. I washed my hands like 5 times, put the circuit board in a plastic baggie like I was picking up after my dog when I was finished, and even trimmed my nails (I read the biggest issue is ingesting residue that gets under the nails). I also wore a full face respirator. I bought it a while back for another project, but realized I bit off way more than I could chew and backed off, so using it here was more of a way to get my money's worth out of it. It does keep me from touching my face as I'm wont to do. It has an eye shield and it keeps out the fumes from the rosin, so it's not totally worthless.

2. the CCTV really helps me see the joint I'm working on, but I completely lose track of the big picture. It's hard to guide the solder down to the tip of the iron to melt onto the joint, and it's hard to keep the tip of the iron tinned. That stuff oxidizes really fast. Parts of it were blue when I was done.

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3. I clearly need personal instruction by someone who knows how to solder blind. There are tons of videos for sighted people to learn to solder, and a few blog posts and articles about blind soldering, but they aren't enough. I also think I'll need a better iron. A $17 kit from Amazon isn't going to cut it. I also noticed the hot iron doesn't radiate much like a stove or oven element. I was expecting to feel heat coming off of the iron given that it's \~700 degrees. On the bright side, it heats up and cools quickly. I did burn myself once, but on the meat of the hand rather than the finger.

There are tools out there to hold your circuit board in place. It looks like some sort of base, a few movable arms, and alligator clips. Some also have a magnifying glass attached.

Two thoughts. First, they sell solderless headers for the raspberry pi if you don’t feel up to the task, they’re affordable and a good alternative to soldering.

If you do choose to do it, the fumes should be minimal if you’re using solder made for electrical work, and an apron should not be necessary. You’ll want a work space that can take some heat and a wet sponge to dab the the iron tip on to clean it from time to time. Having just done this exact task the other night, I would recommend the sharpest, smallest tip that you can find for the iron for getting into all those tiny spaces - I wound up needing to pick up a new tip for this purpose, the chisel tips that came with my iron were not fine enough to get in there cleanly.

One other tip that really helped was to take a piece of masking tap (plastic based tapes will melt if you get the iron too close) and tape the header block in place, then solder a pin in each corner. Then you can take the tape off and do the rest, but it really helps to not have to hold the header block tight while you’re soldering.