Airbrushing

I never weather my rolling stock.
But it shouldnt be too difficult. but really you barely need an airbrush to do it. too many people fall into this trap. particularly with steam loco's chalks and pastels are far more convincing.

Unfortunately the above statements are largely misleading. I do a great deal of weathering, and the addition of an airbrush to a 'weatherer' makes the task far easier and gives more realistic results overall. The airbrush give very fine control over paint application, this is crucial if you are building up layers of grime like brake dust on a diesel. For steam locos there is no better way to apply the sooty deposits that fall quite evenly along the top of the locomotive. However there is no realistic way you will replicate grease and oil creep stains with chalk or pastel, you need paint for that, pure and simple. I use artists pastels for a lot of my 'powder' work rather than weathering powders. The reason for this is that they do not have the greasy finish that some weathering powders do.
http://greengoscalerail.fotopic.net/p32472601.html
This is a standard Bachmann WD, the only additional work it has had is that it has been weathered from the pristine factory finish.
From the general toning down there is quite an amount of work replicating both grime, oils and liquids that cause weathering, and there are numerous techniques that work including application by airbrush. Theres no easy answer to what I do to a model with an airbrush if asked to weather one, as it depends on the finish of the individual loco, just as theres no hard and fast rule on if a satin/matt gloss coat is required to work on. Going from first hand knowledge and images is the best way to weather items, working from actual examples.
http://greengoscalerail.fotopic.net/p11213351.html
To do work like this without an airbrush is almost impossible

Pedro an aerosol can will not give you an even covering as they are not controllable enough, and you cannot get into small restricted areas with them for this very reason. Make up brushes are far to big too also giving little controllability, when using pastell I apply it with No1/2/3 sable watercolour brushes, which are time expired from painting duties.
http://greengoscalerail.fotopic.net/p35213895.html

You may not be convinced by the 37, I'm not sure what that means but bear in mind the size of the enlargement that that image has gone through, it was also take in artificial light which doesn't help the color cast. Whats not convincing about it? It was done from a photo for the purchaser, I only ask as you're the only person that I've heard that comment from, and hailing from the RMweb lot, they're not usually shy about coming forward

Aztec are excellent brushes, there are no issues with the plastic ones they are solvent friendly. They are widely used by the military and car modelling fraternity, and I'm waiting to get one. The last thing they are is a gimmick. The interchangeable nozzles are reported by my brother to be brilliant for speed of work and cleaning, its plenty robust too he's been in the states for many years now and had to buy his after he left his badger in the uk, wonder who got that then? .
As far as masking goes in the past I've used masking tape and selotape, taking the tack off my placing it on my jeans and pulling, never had any fluff issues yet. However the best masking tape bar none on the market is that made by Tamiya, and I've been using it for years. It's formulated for model makers and can be cut, bent, pressed and cajoled into pretty much any crevise you desire, and gives fine lining too as its so thin.
For my sharp edges, for the past six or seven years I've used the Tamiya tape, and then then use high st masking tape and newspaper, (depending on the model size) for the overspray areas. I'd never go back to the selotape now though, but still use large masking tape desensitized on my trouser leg!

Had to think about this one, been a while since I did any vans. Assuming its a BR standard bauxite or grey van, I do the chassis first. Mask the body and roof, and get a good quality masking tape like Tamiya for the edge. You can 'fill in' the larger areas with a cheap tape or newspaper. I then use Halfords matt black acrylic car touch up spray. Gives a nice even flat coat. Needs to be held at least 9 inches off the model though, and do several passes with it. Too close and you'll flood the details of the chassis. This will dry in 15 minutes or so. I then reverse the masking using the solebar, (usually where the colour change takes place) as the fix for the masking tape. With a quality tape like Tamiya it can be cut and placed on some of the fine detail without a problem, as it's low-tack. Then I spray the body colour, wait till that dries, remask the body and do the roof. Once that is dry all the masking can come off and then I'll touch up any areas that need it with a paint brush. Areas for transfers are given a high gloss coating to help adhesion and hiding any carrier film. After transfers are applied then an overcoat of matt (or rarely satin) varnish seals them in before weathering.