I straight up followed my Preceptor approach - sponging on Colvin & Co. Gamboge [again, no longer in stock.
I left plenty of the Burnt Sienna showing through to take advantage of the under rust.
Added some VGC Sun Yellow sponge highlights and then picked out the Mechanicum symbol and used my Burnt Umber ot make the skull grimdark, like my Servo Haulers.
The top was only lightly sponged with yellow as I've seen plenty of examples of construction vehicles, car bonnets and flat surfaces where this weathers most. It's not perfect but I like the result so far.
Lots of details to pick out on the skull, dials, wires and all the reactor insulator glass. I'm slightly regretting not finishing building my Thermic Plasma Conduits. They would have been in the same scheme and it would have been really good to have them painted at the same time.
Still, too much as a batch can stall progress, rather than helping move things on. There's not actually too much to do on this now but it's certainly a nice interlude. I'm just really enjoying being a hobby butterfly - go with the flow!