Two questions:

1.) I'm trying to add a rumble region to a map, but I'm not sure what to use for the rumble class name or the effect name. I couldn't find anything in the docs or in the assets. Does anybody know what I need to use in each section (specifically for engine rumbles)?

2.) Is it possible to change the rate at which clouds move across the planet in space skydomes?

Ignore the effect (just put in a null value). The rumble class, I'm pretty sure, is just referring to the .odf that defines the rumble (e.g. hot_rum_caves.odf). I don't recall exactly offhand, but an easy way to check is just to open up the stock Hoth map and see how its rumbleregion (in the hangar) is defined.

Yes for the rumble region you have to put in a hot_rum_caves object at the location of the rumble (actually could be anywhere on the map really but putting where the rumble is to take place is neater)
Once you place it you have to give it a name in the Name box (example Hanger is one used in Hoth)

You then have to create a region to cover the area that you want the effect to be felt.
Once you have created it and sized it in the box on the right side of the screen when you select the region you need to enter
Type rumble
Rumble Class hot_rum_caves
Particle Effect Hanger (this is from the example from above but whatever you named it would go here)

Munge then get ready to rummmmmmmmmmmmmble (sorry couldn't resist)

Thanks, the effect works now.