Step 12: The final two centers!
Now, there should be only two different colours on the unsolved sides.
Using the algorithm for moving those pieces around(Ll' U2 Ll), get as many of the colour on its respective side. In my case, I am getting as many blues on the blue side, and reds on the red side as humanly possible. The inverse also works, and on the right side. Possible algorithms are:
Ll U2 Ll'
Ll' U2 Ll
Rr U2 Rr'
Rr' U2 Rr
If you have a case like in the second photo, you need to get the red center on the red side, and the blue center on the blue side. Then, align them as shown in the picture, and perform this set of moves:
r U' M U r' U' M'
(M is the middle, rotate it in the same direction as R)
You may need to repeat this multiple times to solve both parts, but after they are solved, we move on the the most time consuming part of the cube: Pairing