Stage 1: Top of cloud
This (for me) is where the main shape of the cloud is created. You can make it random and bumpy, small and smooth etc. You have a lot of freedom with clouds bcoz there is no set shape to them, although there is almost a stereotypical cloud in this game I find. Use the snap tool and just make a bunch of small circles like so:
Keep up a random selection of circle sizes, so that it doesnt look repetitive and monotonous: You wont ever find that in a cloud.
Stage 2: Bottom of cloud
You can do all sorts of bottoms for your cloud; from just a flat line, to just kind of repeating what you have done on the top, to a mixture of straightness and some circles. Here are my examples of them if you dont understand:
Flat line:
Circles:
Mixture of both:
I personally use the 2nd method, as I feel it looks better.
Stage 3: Shading, adding more clouds
I personally rarely if ever shade, so I wont give any tips on that front. However, I have lately been adding in some more clouds to the center of the cloud, like so:
I hoped this helped!