So I don't know if I'm boring the pants off you all, but there may be some people who'll find this helpful.
So what you need to start with:

4 paints: Citadel Grey Seer, Citadel Corax While, a white primer, and Citadel Apothecary White (not pictured). A large rounded-end brush, available from art shops/craft shops. They get beaten up, but keep on ticking. Oh, and a rag to wipe paint on - I prefer using cut-up bits of old towelling.

So here's a comparison - the Shadow Hawk is just primed in Grey Seer, while the Thanatos has been liberally brushed with Apothecary White. The Thanatos is darker, but that provides the detail later.
The quality of the prime coat really matters. The Apothecary White has to run & pool and surface-tension into all the nooks and crannies. Don't fret if it pools on the flat, we'll fix that later. Normal primes have a slightly gritty, chalky surface - this will hold the contrast in place, and it won't work as well (I've tried.) If you need to substitute for Grey Seer, try a semi-gloss light grey, mebbe.
Corax White is white with a little blue added, giving a cool colour. Citadel's other white has brown added, for a warmer look. I like my mecha cool. The primer is just white white.
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If you haven't dry-beushed before, just get a little paint on the brush, then wipe wipe wipe until you don't see any colour coming off. You can see there is a little paint on the brush.

Then wipe the brush over the mini. Don't push, a light swiping action will do you best, and not fill in the panel lines. One brushload got be through about 1/3 of the Thanatos - see how the mini's top right is lighter than the lower left? That's what the drybrush lays down. Rinse repeat, keep going until you feel you've got sufficient coverage & covered any flaws. Remember, that brush has to be dry - so one tip is to always start on the back of the mini, so if your brush is too wet/loaded, no-one will see it

The good point is the paint drys sufficiently fast you can just keep going over & round until you're done.

So there's the mini with the initial drybrush finished. It's white, and you still have the details picked out.

Then the magic happens. Make sure your brush is dry - if it's damp still, this stage will muck up. Get a little
of the white primer on the brush, then wipe it down like before. Then do it again. Then do it until you swear there's nothing coming off. This is the ghostbrush stage. When you wipe the brush over the mini, the paint will come off on the edges, not the flats like before. And it lifts that flat white into something nicer.

Now for advanced idiocy! I decided to do Dawn Guard. Yes, I know ... but I had a lot of DA Feddie vehicles & BA to pair them with. And it lets me mix bigger IWM sculpts - like the Thannie - with KS minis when Wave 2 hits. So here I'm brushing on Citadel's contrast yellow (Naazdreg, IIRC) over the white base. And unlike before, I want a thin coat - if the yellow pools, it looks orange, and I don't want that. So I'm using a small flat brush, and trying to be reasonably careful (but slips can be fixed later).

Then I've done a drybrush layer of Phalanx Yellow over the top of the yellow contrast. This flattens the colour, does provide some highlighting, and IMHO makes it look more BattleTech-ish.

And here he is ready for basing. Metallic bits painted black, then drybrushed Leadbelcher over them. I then used a small/medium brush to drybrush Corax White where I needed to clean up - this covered any metallic misses, and let me straighten up the edges of the yellow. Tipped the lasers, must go back and colour the PPC muzzle, but getting ready to fight for Julian Davion.
This took about half an hour work time over a few hours, while doing other things. This I find the joy of big unit painting - you just keep moving, you do different things between stages, and it flows. Yes, there will be boring bits (eg. priming everyone), and periods where you have to wait (for the contrast to dry), but I usually have some sub-jobs percolating through at the same time (eg. proof of concepts for the next few units).
Anyway, no Golden Demon or CSO artist, but if you want to field white on your table, have a go, and share your experiences!