J.H.
This is how I learn everything! (Not necessarily rap, but with music.)
I think it's worth a shot. What's the worse that can happen? You spend a little bit of money, find out it doesn't work, and move on to the next idea?
If it helps, I still remember the bones of the body because I put it to jingle bells. I had just moved to a new school and had 4 days to learn them before the test. It was almost Christmas, so I started singing Jingle Bells while studying. Next thing I knew, I was singing the bones of the body to the tune. Test day came around and I started humming it quietly to myself. I got a 100%.
Good luck!