Originally Posted by allset2travel

I may not be directly offering suggestion or advice, but just a data point.
I had a very similar situation. My DONEx first flight (on CX) arrived at HKG. By plan, I had a very long layover (can't recall exactly, but it was several hours) before my next CX flight. While inside Wing First Lounge, I handed a spreadsheet with all flight details of changes that I wanted to get done (make sure all flight had D availability). The agent called another agent in the HK office. She then told me to just relax.
Long story short, it was all done according to my spreadsheet. We were in the lounge for a long time. During which an agent kept it informed of the status (being worked on). When the first agent went off duty, she introduced me to the next agent who was to "take care" of me!
I think your 3 hour layover maybe tight (even if YYZ-HKG is on time) if you want to get it done at HKG by CX. I might say, I was happy with CX's performance as being professional.