Frankly, CLRS goes over a lot of the basic knowledge you need to get through the book. I don't think a discrete math textbook will help you if your main goal is to get through CLRS; the math in that book isn't that dense. Like all things, it just takes practice. Spend a lot of time on sections that are hard to understand, and future sections will become a lot faster and easier.

Try the MIT algorithms video lectures: http://ocw.mit.edu/OcwWeb/Electrical-Engineering-and-Compute...