Interesting kit, I'm following.
I've mixed Tamiya gloss black and flat black (acrylics) to get semi-gloss, though I prefer their actual semi-gloss which lays down very nice. However, I find semi-gloss to still be too flat for chassis painting. For general chassis parts that are to be black, I mix Tamiya semi-gloss black and gloss black acrylic to create a black with a slight sheen, perfect for chassis work. I call it chassis black, and always have some on hand.