I'll post more pictures of my painting-and-staining progress (boring part), but I thought I would update my findings to the questions I asked. Maybe useful for others.
1. Yes, the brush strokes do fade. I have 4 coats of spray paint and I will be doing at least one more. I'd still recommend a spray undercoat/primer.
2. With the Tonerider pickups, I think you use the springs OR the foam, since they are really doing the same thing and allowing vertical adjustment. I will use the springs aswell as placing some foam under the pickup and between the body for a bit more stability.
3. Wiring. What a pain. My soldering mess looks like someone combined spaghetti with lumpy concrete and threw it against a wall. Next time I'll buy some new solder and probably a new iron, as I think mine is pretty done for. Even though the pickups only have one wire, I have had to cut, peel back, twist, tin and solder the mesh shield as the earth, which being quite thick, was a real pain to solder on the back of one of the pots, especially alongside the 2nd pickup's earth and a couple of other wires. Hence the lumpy-concrete-solder job.
4. Gave up on the wires supplied, so used some old 'standard' wires I have lying around. Seems to do the job. Again, the wiring is all "theory" at the moment, as I haven't tested it as yet, so if you're in Inner West Sydney and your lights flicker sometime later this week, then consider this build 'complete'!