I did my friends cover and mothers is good towards the end of the job but i would start with something a little more abarsive to begin with , i have this stuff taht is called blue magic its really good all around polish.
dont buy mothers plastic polish whatever you ddo, a horrible product, it sucks....but i just use the brocks that come in polishing kits and use a die grinder witha polishing attachment.
yea mothers really is more of a finishing polish IMO. You need to work through different grits of different compounds in order to actually polish the clutch cover, you can purchas various aluminum polishing kits off the net. Start out my sanding the finish off of the cover than work through the grits in the kit. Take your time if you want it to look nice.