Pastels

Pastelsneed to be sanded down into a fine powder on sand paper then brushed on to the model. After that use a coat of matte varnish to seal them to the model.
For the washes I use artist oils thinned with mineral spirits. I go over the whole model with a wash then after that has dried I'll go back and add washes to specific areas that need more of a wash. After they have dried for a few days apply a coat of matte varnish because the wash may have a glossy look to it. After this has all dried you can start your dry brushing.
Good Luck,
Pat

I can't argue with any of the advice above.

As for the pastels, stay away from oil based pastels, they are practicaly useless for any endeavor in the modeling hobby. They're messy, greasy, they don't ever dry to the touch and they react very unfavourably to any sealand coat you may try to put over them. All this on top of the fact that, because they never really dry, they are dust magnet areas on your model and once the dust is on them its on them for good, its not going anywhere, in the space of less than a year, you'll want to strip all the paint off your model and do it again differently just because it looks so bad from the dust.

On the matter of simulating dust on your models when you really want it there, chalk pastels are your best friend. You do have to grind them up very finely, but they do dry brush on to a model very nicely.

Good luck!

It is beeter to use dry pigemnts and fixers. It is more realistic and gives a natural texture on the model that pastels can't achieve.

I use pastels myself and enjoy the easy water clean up and non-toxic fumes and odors. Here is a video from youtube demonstrating a pastel sludge wash. If the link doesn't work copy and paste it in your browser.

https://www.youtube.com/watch?v=QrCueONhuko