robo, you may be ripe for the new form of note-taking called Bullet Journaling. I have one in a book I was given at work, bound and with an elastic loop from top to bottom on the back to keep a marker at the current set of pages. It's not the neatest method (the way I do it), but I use it to keep track of various things, not just the declutter project. Actually, when you ask this, I could add notes about my eBay sales that I haven't documented anywhere. If I were to be more businesslike instead of a hobbiest this would be a good starting point. I'd go for the bound book.

Look at places like Tuesday Morning, Big Lots, used bookstores (in several states you'll find Half-Price Books) - I've been seeing these with a couple hundred bound pages for about $5. They're durable enough to use and carry around every day.

I use this as a calendar, an appointment book, to keep short lists, to make quick notes that I want to keep and not have to hunt around later for the piece of paper I scribbled it on. It usually ends up with the left page for the calendar, the right page for the task list, the next page for more general outcome notes, and the second right page for other stuff, I just label it "notes." So four pages per month.