I reduce the 5x5x3 to a 3x3x3. 3x3x3 edges first, corners second.
This is pretty straight forward. I have not looked at rline's tutorial, but I'm sure I do it differently.
In 50% of the solves, I'll see two corners need swapping. A single U turn transfers this to a situations where I need at the end something that looks like a swapping of two edges.
I'll use a cubic 3x3x5 to show it. The proportional one is logically the same puzzle!
I scrambled the puzzle and reduced everything less two 3x3x3 edges.
Actually, I do a 3-cycle where I involve a third 3x3x3 edge that has one of the two edge colours of the swapped pair. After the setup using 3x3x3 turns only, it looks like this:
We need a counter clockwise 3-cycle of the outer U layer.
Here is a cuboid sequence that does the job (Please note that U is just the outer thin layer and does not involve the layer below. R is the 3x3x3 face R):[(R2 U)x2 (R2 U2)x2]x2
(x2 meaning repeat the sequence in brackets twice)
Personally, I think that a few cuboid sequences make your life easier.
I think there is a dependency between the number of sequences you memorize and how hard your strategy becomes.
Think of solving the Rubik's Cube
a) no sequences: pretty hard to invent something on the fly
b) two sequences = Ultimate solution
c) many sequences: speedcuber method
The Ultimate solution is a very good compromise, though.
rline shows how much he can accomplish with it.