As you can see, I'm trying out one of your tips.
The plan is to paint a tab of Liquid Mask where the plastic joins, so I don't have to worry about primer or airbrush spray getting on the joins. After painting, I just peel off the Liquid Mask and glue them together. That's the theory anyway. Check my
IG post about November and see if it worked.
My tip is the foam. You can't line them up and prime them (will melt the foam) but while you're grinding and sanding, the foam makes a great pincushion for your toothpick parts and Dremel bits.