Give this one a try, man (and make sure to try this first on some scrap plastic til you get the technique down):
Go ahead and spray the entire thing Dark Yellow (Dunkelgelb). I use the Tamiya Dark Yellow spray paint, very good match. Leave off the small, delicate parts. You can go ahead and leave off the tracks at this point.
Now here’s the really COOL bit: You take ordinary table salt, some water, and an old brush. Mix the salt and water to a pasty “goop”. Make sure it’s not too watery, you want the brush to leave behind crystals when you apply the stuff to the model. Then you take this stuff and “glop” it on the model. This is gonna be a mask for the white overspray, so use it to cover areas of high wear (top edges of turret, edges of hull, weld seams) or high heat (get it good on those areas near the exhausts) or near the ground (wear and tear from mud drying/flaking, contact with ground objects, etc).
Now, once you get it good and salted up (use your own judgment how much of the whitewash you eanted to have worn off to expose the undercoat), you let the whole thing dry. Overnight is best. Then, you take some flat white spray paint and hit the whole thing again. You let this dry, again I would suggest overnight, and then get after the old girl with an old toothbrush. Scrub off the dried salt, and voila! You have one nasty, ugly, winter-worn old Konigstiger.
You can also use an old toothpick or old Exacto #11 blade tip to fleck off the salt. You can go as heavy or as light with this weathering as you like, and if the salt is stubborn, do some “flecking” and scrubbing under running warm water. Then use the four-part product “Rustall” for additional weathering.
Give it a shot first with an old model, and see what you think. Also works really wonderfully for an undercoat of Panzergrau (Panzer Grey) with an overspray of Dunkelgelb (of course, the transition from Dunkelgrau to Dunkelgelb occurred before the Konigstiger was in service in numbers). I’ve become completely enamoured with this painting technique, and once you see the results, you’ll be awfully hooked on it as well).