The grease stain on a black keyboard looks awful. What are the recommended steps to remove the grease?
I have found some posts online suggesting pure alcohol as a solvent. (one such CNET forum)
Is this advice trustworthy?
The ideal solution (that I've found after years of cleaning Apple products) is not to use alcohol directly. Instead, mix it with water. The proportion to mix is simple:
I use a bottle cap, fill it with alcohol three times then the same cap with water seven times (you can use something bigger if you want more).
With that solution, you're safe to clean all your mac and the alcohol presence guarantees a slow but secure grease removal without leaving the typical alcohol stain/residue that occurs when you use pure alcohol. Also the low concentration makes it safer against things that may get damaged by the usage of pure alcohol like rubber compounds or human skin.
For occasional cleanup you can use the simple, free and excellent Keyboard Cleaner. All it does is make your screen black (so you can clean it better) and lock your keyboard so you don't trigger accidental keys while cleaning. Of course, you can always shutdown the computer too.
Regarding products like iKlear and such, they are ok, in fact I'd recommend you always get a bottle of iKlear around, it's good to have and their small wet towels are very handy for quick clean. Remember never to use toilet/kitchen paper, use instead any "approved" cloth (like iKlear, TomBihn, etc.) the "micro fibers" are designed to not scratch your surface.
I wouldn't use pure alcohol.
Alcohol is the best answer; it dissolves grease. Power down, soak a cloth with isopropyl (at least 70%), and gently rub the keys until clean. As an added bonus, the alcohol will kill the germs on the keyboard, which are notorious for collecting them.
As you can see in the article How to clean Apple products, alcohol and ammonia based cleaners are specifically not recommended for displays and iOS devices, but not listed as problematic on portables and desktop machines.
Try a silicone keyboard cover from kbcovers.com. These work great with typing, keep dust and debris from getting between keys, and also prevent the keys from getting greasy.