While I thought I was going to spray primer and was getting things ready, I found I probably should assemble some of the parts together before spraying. And I found that there are 2 vertical uprights in the middle that supports the rear wing.
Normally, I attach a nut to the base to mount the car to the display case. This time I got lazy, got myself a hand tap and cut some threads to the white metal. It's not ideal since white metal is so soft and the threads may get stripped. But then I felt that's too much work to grind drill and attach the nut. I can always find myself some excuses.
For the other tiny little piece, they're already on toothpicks or got "clipped". Since I have to use oil to tap the holes, the base needed some rinsing to get rid of the oil before painting. Now I am waiting for it to dry.