Okay guys, (and gals)
You gotta know where I'm coming from on this one. I've been on armored vehicles since 1975 (ouch!) and really like the look of them in the field. I think the best weathering I've seen on a model is in that ad for the airbrush(?) with the rear of a Tiger I.... very NICE, it's in FSM this month, take a look. Faded, dirty, but filled with detail.. wow!
Now, to me, a clean, lightly weathered vehicle (as in the article, NICE build though, don't get me wrong!) means one of two things. First, it's in the motor pool, off the wash rack, or on parade or inspection, my Paladin is that clean right now. Only in the driest of weather does my vehicle stay clean and that's not for very long! Dirt will gather under the sponsons and fenders even in the driest of conditions and mud us just wonderful! Wow, all that stuff thrown twelve feet or more (four meters!) into the air on the trail.. !!! Love it.
Anyhoo, my driver will wipe only the dirt away that he needs to in the field in order to either check suspension, lube points etc, or perform other maintenance. He has other work to do when he's not doing PMCS (Preventive Maintenance Checks and Services), so if I saw him scraping dirt from road wheels or worse yet, tracks, without meaning to replace them (or check a suspected loose nut), I'd have a talk with him. In other words, dirt doesn't mean poor maintenance, it means use in a fun environment. We don't really, thoroughly, clean the vehicles entirely until the wash rack after days (or weeks) in the field... or if we find a REALLY big puddle!!
Try putting some mud up under sponsons and fenders, behind the road wheels and under the front and rear of the hull where it splashes a lot. It won't hide any detail, but will make your models look as if they've been in use (They'll even have that type of spatter if moving into an urban environment)! Not that they don't look nice without heavy weathering... just in case you want to, you know, muck it up a bit.
Another two cents.
Ron