A bit unrelated, but I have the same soldering helper as in the post. It's called Omnifixo (I found out about it from a YouTube video (Norm from Tested)). I was initially skeptical, but it's made soldering a whole lot easier - highly recommended.

I've done some mouse PCB mods myself (swapping dead switches mainly). My biggest annoyance is resoldering through-hole components - unfortunately aftermarket PCBs for mice are quite rare, and my favorite mouse isn't all that popular in the "mouse community".