For Alucain, I managed to get his success ending in about 3 tries? I followed the advice of having more than 10 INT before the completion of the project. I also spent most of my time in the library, and I suggest when the tutoring pops up, you choose it as it's often Alucain who tutors you then right after that choose the library again to work on the project with Alucain. Just keep on repeating that sequence and you'll get his success ending.