For small jobs like that I just purchase a couple of tins of compressed air from the pound shop. The "straw" provided with the tin makes it easy to precisely direct the air. You could always hold the vacuum cleaner hose under the heating element to catch the dust. As wayners said, a brush (and possibly cotton buds) will help.
If you use cans of compressed, do not shake them first and wait a minute or two before turning the power back on.