A chip puller works nicely to pop the keys off.
Failing that (I lost my chip puller), bend a heavy-duty paper clip into a U-shape and use needlenose pliers to form very short gripping surfaces, about 1/16" to 1/8". Use it just like a chip-puller.
This is about the only way to get the keys really clean as well as clean crumbs, ashes, etc., under the keys.