I'm purging and sorting old contact information and I find I get small chunks done when I'm sitting on the phone on hold, or waiting for a meeting to start or when I feel low energy, even. It's something that takes less brain-power than most other tasks, so I just slot it in wherever. Somehow that works... it feels like alchemy, but it works.
And it doesn't sound like you have a looming deadline to get them all sorted, so that's in your favor, isn't it?!?
I have NO idea if that helps you at all, in fact! Long day, brain out of gas...
constant forward pressure