I want to have a crack at using weathering powders to dust up a M977 HEMTT I'm building for a diorama. I have never used these powders before and would welcome any ideas or tips on how to get the best results from this technique.

Thanks
Vihuri

There are a few ways to do this. The way I prefer is to load up a flat head paintbrush and brush on the powder / chalk / pastel. Of course it depends on where you want the powder to go, but dust thrown up by tracks would be upward from the tracks and angled towards the rear of the vehicle. Settled dust on the top of the deck would be slight but plenty in and around the nooks and crannies.
Less is more but you can overdo the effect unless it is a desert vehicle.
The advantage of pastels / chalk is that you can remove the effect if too heavy with more brushing.
Practice and get as much reference as you can. Go to your local building site and ask to see the Earth movers there. Be careful though and go with an adult if at all possible.

HTH

I'm with Desert-Fox on that. I prefer to use powders that I buy for peanuts at local arts craft stores. For 10 bucks you can buy a ton of them in different colors that you can mix as you wish to obtain infinite shades of colors.
If you're intersted in the results have a look to my post here:

https://armorama.kitmaker.net/forums/9091&page=1

where you can see an M47 before and after.
Ciao

I'll chime in about rust here, which tends to streak down from all rusty spots due to water flow. I will paint a small spot (less is more) with a rust colored paint, usually model masters before I paint the base coat, and I will leave a small bit of tape to mask it. After I paint the main color and remove the mask, I will mix a similar color of pastel chalk and lightly streak the chalk down from the chip. Be sure to follow the natural contour of the vehicle and don't over do it.

There is also Mig Jemenze's technique for rain streaking, which can be found here:
http://missing-lynx.com/rare_world/rw01.htm
There is info there on using chalks as well as paint for this effect.

Rob

Don't be afraid to mix them to create custom colors.

You can also add water to make a custom wash color.