I know it's boring, but my advice: don't bother.
Chemical tinning is messy and stinky and usually expensive (or hard to get the chemicals).
Solder tinning (with solder soaked braid, or with spreading paste on hot PCB) is tiresome and frustrating (bridges!) and finger burning and too easy to overheat and pull off a pad, and ruin your day, and it always ends up looking like crap.
Just tin the through hole pads using iron and solder as it makes it easier to get a good fillet, for the surface mount ones, just solder as you go.
Spray lacquer after assembly (protect anything that it might affect) if you want better protection against the copper oxidising.