I have a nice new double road engine shed for steam locos.
Consequently I need to make it look less new without going to extremes. 

So what's the best way to dirty up a new steam engine shed to make it look a bit more realistic?

Any suggestions/advice most welcome.

Ray

Without going extreme, weathering powders, chalks etc are quick and easy. Loads of tips and techniques are available if you search on youtube.

Find photos of the real thing which have the atmosphere you like, and have a go at replicating those scenes.  I like to use weathering powders and thin washes to add grime, dirt and rust effects.

I remember seeing Guildford MPD around 67-68 and basically there was just dark grey soot and filth every where, it looked a pretty dismal place!

This picture represents it well but my memory tells me it was a shade brighter probably the exposure of the film doesn't do it much justice!

@honestjudge @ntpn @Mr Sprue
Thanks for the suggestions guys but I hadn't explained my dilemma properly.

With a lack of skills and deteriorating eyesight I'm not into detailed weathering.

Im really looking at a way of taking the obvious newness off the model by making it a bit grubby and therefore a bit more realistic.

I'm wondering if thinning down a matt grey acrylic paint and applying (in differing depths of colour) over the complete model would be a suitable approach?

I bought some HUMBROL washes in the hope they would do the job but they are really for highlighting detail.

Ray

I would go for weathering powders. You just dust them onto the brickwork or whatever surface you're working on. If you get it wrong then can be cleaned off.  You can get sets of useful colours such as rust, grime, ash etc.