Batch #5 is:
5 - BS spacebars
18 - BS single units
4 - DCS single units
I spent last night taping and sanding and priming this next batch. It's not my largest batch to date (that was the first, flawed "bathmat" batch) but it's a lot of work, and think these are better. First, everything gets a wash, then when dry I tape the spacebars, then sand the exposed areas, then mount them on their cardboard skids. The single units get sanded on all sides (surface is textured already, so not needed) along with the edges and corners, very lightly.
After sanding everything gets a rubdown with a moistened paper towel, then a quick dry, and then I mount them to their skids. The spacebars all get their own skid, but I put multiple single units on a skid. This makes priming and flocking them a lot easier, because you don't have to touch the keycaps, you can just manipulate the cardboard.
I notice some other people paint keycaps -- how do you make the keycap stationary while painting?
When it's time for flocking, the spacebars stay on their skids, but the singletons I cut apart. I do one at a time; coat it with the adhesive, and then electrostatically flock, then set aside. That's for tonight. My breakdown is going to be two black spacebars, one sage green, and two in the magenta color, then six BS singletons of each color, and the four DCS will all be the magenta.