I have rescued such items many times using only sandpaper, scrapers... such as tiny screwdrivers, or pencil erasers. So far I never had to resort to chemicals.... but if you do, a Q-Tip is a good way to apply.

I do, however recommend getting totally away from alkaline batteries now that GOOD rechargeable batteries are available.,,, such as Eneloop by Panasonic. They are more expensive to buy, but rechargeable thousands of times! I have 'almost' totally switched over to them for small devices...