They are hard to perform only if you don't know how to do it. I know Kabal, Kung Lao, Scorpion, and Sektor. All the rest I have some trouble with.

Your best bet is to turn on One Button Fatalites on the PSX version of MKT. But the only problem there is that you can't have the satisfactory of performing a long button combination.

the only brutalities i know are rain and noob saibot. the only reason i learn those is because that was the only finishing move they could kill with on umk3 on genesis (i had to settle for that til i got mkt on saturn) if it wasnt for that i wouldnt know any of them either. and i got a guide to mkt with them in there smh

A little trick that will help when perform the Brutalities is to do the first few hits real quick. For example in Rain's press HP, HP fast, then after the first few hits slow down to a moderate pace, then always remember even if the Brutality says it ends with LP, LK, HK, or BLK, always end in HP. Almost every Brutality in every game magazine says to end in a different button, but every Brutality should start, and end with HP, and every Brutality is excatly 12 hits long before the CPU takes over. Ermac's Brutality is the only aception. His is 15. No matter how many times I've tried the 12 button one, it never works. So here is his correct one:
Ermac's Brutality
HP, HP, LP, BLK, BLK, HK, LK, BLK, HP, LP, LK, HK, HP, BLK, HP

Hope that helps a little!