Well this is not the last word in painting vehicles but this is how I do it ....Get ready this could be long.... :-) Okay I start by painting the whole thing black (for dark colored vehicles ) or dark brown for sand colored vehicles ..I don't use a primer ....second I take my base color and spray the vehicle panel by panel ..getting very close to the sides but just letting the preshade color show through. When I have gone over the whole thing ,I reload my airbrush with my base color lightened up (i use dark yellow for OD vehicles )or white for sand based vehicles....add about 25% of the lightening color to the mix..I then reshoot the vehicle panel by panel lighter in the middle but I will go right to the edges of some panels ...when you finish you will see a very faded look to the tank ..I usually do one more coat even lighter but that all depends on the look I'm after.... Once this has all dried I will add a coat of Future over the whole model... If you have decals to add you might want to put them on now or after your wash ....I use dry transfers or masks as much as possible . If you add decals make sure to add at least another coat of future over them to protect them from the weathering ..dry transfers should be protected too . Next thing I do is add a couple of filters...On OD tanks these can be an olive green color ,dark brown ,sand color ,or any color you really want to use ....these filters are very very thin washes...95%thinner to 5%paint...This is done all over your kit and is hardly noticable but it is there and does add depth to the paint. I use lighter fluid as a thinner ...I will then use the more conventional dark wash of Raw umber or burnt umber mixed with black 75% thinner to 25%paint . This I use more in the deep cracks and around details ...If you have decals on your kit be careful if this mix runs around your decals they will show up more than usual..Once all this is dry ..shoot your flat coat all over ..Polly S works great...I do two thin coats instead of one heavy coat. Next thing I do is creat a rain streaking effect on the paint ...I take out my oil paints and use all kinds of colors I use black ,burnt umber raw umber ,burnt sienna ,yellow ochre and white. I put tiny spots on all the verticle sides in no pattern what so ever ...I then take a flat paint brush ..dip it in my lighter fluid I wipe it off a bit on my cloth and the drag the oil paints downward wiping off my brush often ...this is very subtle but will really show up later .I don't put too many scratches on my kits yes a bit around the hatches but not too much...I will add some lighter scratches of the base color here and there ...I use a mix or burnt umber and black for some scratches around the hatches ..I wil use a pencil lead on some corners and for the wear ..just a bit .. I hardly ever drybrush so I guess you'd do it before the scratches .
So that is about it ..it sounds long ..and it can be ...but it is so much fun watching your kit come to life ...try some of these techniques and if you have any questions just p.m. me or ask here . If you want to see some of my work take a look at ...http://www.nutsnbits.com/rcraig/
sorry for being so long winded I hope this helps you out a bit..
all the best
Rick