I use oven cleaner to remove the carbon in the exhaust ports. becareful not to get oven cleaner on any polished surface's, as it will tarnish to shinny finish.
Also for general clean up, wait for the wife to go to work, then run them through the dish washer. Tech tip: dont try and run them with full load of dishes, and run the dish washer through one cleaning cycle empty, before the wife get's home!