All in all, this was a kind of long wound but very rewarding project. I learned a bunch of new stuff and now have Ideas how I could do it even better next time.

What I learned:

• PIC ecosystem (software, programmers, tool chaines, a bit of history as well)
• Using solder paste and SMD stencils
• placing SMD componets
• PCB reflowing with a hot pan (it is possible, and actually works quite well)
• cleaning up flux residue

Specifically, what I want to improve is:

• try out hot air rework stations, possibly get one
• get brushes or other better tools for cleaning up flux residue / possibly even get better flux
• ...

What remains:

• finish up this write-up
• put them into small waterproof containers
• possibly fork the git repository and push additions to calibration.py
• possibly try making a nicer silk screen with markings for the LED polarity (might require EAGLE :/) as not to mess with Ted's original files

Some pictures of my finished fleet: