Bobbaily, for this one and others which require tire painting i tend to use black so i dont have to paint the tires again but normally i use red oxide seeing as this was a common primer if any shows through it can be justified heh but any primer would work to be honest.
SMJ, what you saw in the pic was straight van dyke brown oil paint the sheen on the edges is a by product of the washes buffing the paint edges (i work the washes around a lot) as far as technique in applying the paint its just applied with a scrap of sponge around edges and places i imagine would get scuffed i have a couple of articles showing this kicking around. when i prime the models i do it in several coats using a rattlecan from every possible angle then i look from every possible angle to see if anything was missed if it was i touch it up if i cant see anything then noone else can either so i dont worry about it kind of like not painting the interior because why bother worrying if it cant be seen :) setting the airbrush to fine and getting close will prevent much overspray onto the tires and weathering or a quick touchup takes care of the rest.
well i have an update,
first a closeup of the turret for you SMJ note that most of this weathering will be lost but i did it just incase
and an overall view
next i gave the model a coat of future then several coats of hairspray (i recommend at least four coats of arosol hairspray)
then the whitewash was airbrushed on (be sure to use acrylic paint if trying this)
then i began wearing down the whitewash with a brush and water i intentionally went for a very worn look ultimatly for a springtime dirty tank but this method is very controllable so you can do as little or as much as you like
in progress
and all worn down
time to weather the whitewash i started with washes of black and van dyke brown
after a few more washes and i was happy with the look i worked on some of the details and began with the pigments
i followed the pigments with more washes to blend them and tone them down
next up will be dirtying up the lower hull and tracks.