The powder was probably baking powder mixed with CA glue - a home recipe that's used as a filler. Not sure how he attached the parts to the sticks for painting - could be butyl or even white glue. No idea what the clear coat was - I don't speak Japanese. But they use rubbing compound to get that nice showroom shine. Use a fan that moves enough air to remove noxious smells and vapours. Search the web for spray booths and see how powerful a fan they use.
What was the powder, was a primer used, how did the sprues attach to the parts and how did they come off, what was the clear coat. Are any of these paints acrylic? Also, how strong is the fan that you can spray without a respirator?
