Main painting. Vallejo model air, Flat white (90%) Neutral Grey (10%) - nominally at least, once I had this it seemed a little light so went with a drop or two more grey. Sprayed on in fine light coats about 5/6 passes per coat. Three coats overall. The underpainting worked reasonably well. Wish I'd been a bit more specific in where I put the black underpaint, but oveall there is a bit of variety added into the grey that looks quite natural. Once I get the wash and some weathering in there I believe it will key things together quite well.
Next step, washes and weathering. This is going to be an Endor AT-AT so looking for rust and tree marks on the legs and rain streaking down the sides.