Also put in the bridge pins. First up I cleaned the paint out of the holes, and cleared a bit of space around the lip of the holes, where the paint had gone in a bit. Thanks to Simon for advice on that. I ended up using a cylindrical bit from my dremel clone, and used it to sand out the holes by hand. Took the opportunity to also clean up the holes for the pots and switch, as the paint had filled them enough that the electronics no longer fit through the holes.

Hammered the pins in, and it didn't chip the paint... but it did cause the paint under the bridge to crack. At least that's what I thought had happened... I then realised that it's actually the wood underneath the bridge has split with the stress of the pins going in. Later on I noticed there's a horizontal stress crack underneath the right hand pin as well.

Well, bugger.

I've filled the cracks with thin super glue, as it really wicks into the gap. Hoping that will be enough to stop any further cracking?

I'm wondering if widening the holes even more would have stopped these cracks from happening. There definitely seemed to be plenty of room in the holes - the central part of the pin well and truly fit, it was just part of the fluting that dug into the wood. I also don't know if I could have drilled the holes much wider, as the top edge of the holes is right up against the edge of the bridge cavity as it is. Any widening of the holes might have stuffed the paint on the top of the guitar. Oh well.