Here is a short tutorial on a combination of settings I have found for rendering out volumetric clouds using PyroCluster in Maxon's Cinema 4D. These are the settings I used on my airplane renders.
Create an emitter object. This can be found in the menu Objects → Particle → Emitter. Create an environment object (When rendering volumetric particles it is necessary to have an environment object, or else the particles will not render correctly), and a Sky object.
Create a simple new material. In the color channel add a Gradient shader that will resemble a sky. Create the gradient based on the following settings with a simple light blue to dark blue gradient and in the V direction.
Create a new PyroCluster shader and a new PyroCluster-VolumeTracer shader. Apply the environment material to the environment, the volumetric material to the emitter and the sky material to the sky.
Change your scene's frame range to -200 to 500 frames (Under the Edit → Project Settings menu).
Select the emitter object and change its Particle attributes to match the picture. Switch to the Emitter tab and change the X-Size and Y-Size to 300.
Select the PyroCluster material and change the density to 150, turn off age effects, change the size to 220 m, change the X scale to 1.5, Y to .9 and Z to 2.3 and check the preview button. Turn on illumination and keep the default settings. Under shadow, turn on cast shadows and self shadows, turn the transparency to 15%, and the ambient color to a light sky blue. Change scale to 900%. On the noise tab, turn peak blend up to 100% and change detail to 5. Turn on no scale.
Select the PyroCluster environment material and change the volume tracer's render mode to User (from Crispy) and match the following settings:
Add in a spot light with soft shadows and an orange color to simulate sunlight. If you have other objects in your scene, and you need additional lighting, I recommend disabling PyroCluster Illumination and PyroCluster Shadow Casting under the Scene tab of the additional lights. The single sun spotlight is enough to illuminate the particles.
Finally, to optimize render times change the ray depth, reflection depth and shadow depth down to lower values, also increase the ray threshold to around 10%.
These are just some settings that I have had time to play around with. There are probably some more tweaks that one could make to decrease render times or make more realistic clouds. Let me know if there is anything I missed.