Correct. What I want to know is how to find what I need as opposed to manually looking through the tens of thousands of entries.
You can filter in the matches window, but it by definition only shows matches, so I'm not sure if that's what you want.
What I would do is use the code browser views (windows titled "Version Tracking (SOURCE TOOL)" and "DESTINATION TOOL"). So if you are trying to find, say focus_busy, in the ixus105 window press g to open the "go to" window and enter focus_busy. If there's a match, you'll see it in the matches window of that source tool, and double clicking there will sync the other code browser. If not, you can start exploring the references in the known firmware to find equivalents in the one you're trying to port.
What is the end address and which function do I patch? Is it sub_FFC00354 like it is for the IXUS310?
Go to FF810000 for your camera, and follow the disassembly until you see the equivalent. The ixus105 starts at FFC00000 where your camera starts at FF810000, but the code should be very similar. Ixus 130 as another FF810000 cam, if you prefer to use that for comparison.