I think that it’s good to dust as much as possible with a soft brush and/or a clean cloth or paper towels, very gently. Then, you can wash with slightly warm water and a little bit of detergent if you think that it will help with the removal of grime on the surface. Make sure that you rinse well your detergent from the glass surface. Depending on the grime, soot and/or dirt accumulated, I will suggest to use ethanol or isopropanol, gently with a cotton swab to see if it works. If your soot is grease the alcohol will remove quite a lot and even more than water. You can mix water and ethanol too (ratios 50:50, 75:25 and 25:75).