Should I paint the parts before assembly or after?Couple things:
1. You can paint over fuck-ups in assembly pretty easily.
2. It doesn't matter how good/bad an individual unit is, only that the army as a cohesive whole looks good.
3. Start with something easy and work your way up to the crazy stuff. You can buy a $5 junk marine and practice on that before you drop $60 on St. Celestine or $200 on a titan.