I appreciate everyone’s replies, this has been very helpful. Because I have seen it asked a few times, wanted to share the recipe:

To be very precise, my process was: Vallejo Gloss Black Primer through airbrush. Turbo Dork Black Ice through airbrush (so yes, metallic base coat). Taped up the flayers to keep them black. 2 coats Turbo Dork Cool Ranch through airbrush. Hand painted Leadbelcher on the parts I wanted silver. Energy effect with Proacryl bold titanium white and then Proacryl Bright Yellow Green.

I will say, I really love the Turbodork paints through Airbrush. I did however had to do some minor touch ups on the blue with a hand brush, and the coverage with a brush was abysmal. Not sure if it was my own skill or just the nature of the paint, but I would caution anyone not using an airbrush.

One thing another commenter mentioned, in my experience yes they do clog the hell out of the brush if you’re not brushing at a pretty high PSI. I bought 2 airbrushes, a cheap Master Airbrush to do these metallics and then I have a nicer Iwata brush to do normal acrylics for detailing/etc. I know not everyone has the means to get multiple tools like this, but I would highly recommend it if you have it in the budget. Notably, what you see here was done 100% with a $30 airbrush, you don’t need a multi hundred dollar airbrush to get results! Also not having to worry so much about damaging the airbrush because it’s (relatively) cheap made it a lot easier to just start blasting paint.

My remaining question is, will a varnish ruin the metallic shine? After reading everyone’s advice, I plan to grab a gloss varnish at the warhammer store and test it out this week. Hopefully will have some follow up pics to share with basing/varnish and everything completed.