Here's the progression on the sandstorm I teased a few weeks ago. I picked at it here and there since:
This was the original drawing I posted ^ which was done in a few hours.
Added some detail rocks, and I was working on making the mouth look more sandy. I put the guy on a horse to give him more of a reactionary pose. I also moved the balloon out so that it didn't get lost.
Small adjustments to the mouth angle, swapped the rocks so the right side wasn't so heavy.
Finally, I added some more horses. I wanted it to look like a group of nomads had been wandering through the area when the sandstorm blew up very suddenly, chasing down the balloon and taking them by surprise.
I've had a lot of people asking how I do clouds. I will try to do a post on that at some point when things calm down, (ahahahaha...ha) but it really boils down to getting or making a good quality cloud brush that you like, then taking a soft-round with a high transfer and very slowly building up cloud shapes. Using a straight up cloud brush generally makes things look cheesy, but the combination of a good cloud brush and hand painting into it with a soft round really gives you the hand-done feel. I don't use photos much for clouds and I really do not care for the smudge tool, I find smudging wrecks more than it helps in my process.