I've used 1mm wire and 0603 SMD leds (1,6x0,8mm). It took a lot longer than expected the idea was easy, the reality hard (and frustrating at times)
Some methods of implementing the LEDs:
Different light positions meant different solutions, some easier then others.
I've kept the drilling and glueing to a minimum of parts (mostly extra parts bought for this purpose) the sets can be brought back in original state without much effort
I'll make an introduction post!