You've cleaned the glass from the outside, with the oven door closed. You've cleaned the glass from the inside, with the oven door open. Now, one thing is clear even if the glass isn't: The grease and grime are wedged between the glass doors. Rather than giving up and disguising the messy glass by hanging dishtowels, maneuver your way between the doors. This is one cleaning task that requires a little ingenuity.
Prepare your long-stemmed cleaning tool for oven duty. A ruler or yardstick is ideal because it is long enough to reach up inside the door and sturdy enough to be moved around within the tight space. Wrap a cleaning wipe or, ideally, a paper towel soaked with a 1-to-1 solution of vinegar and water around the ruler with rubber bands. A vinegar and water solution stands a better chance of removing built-up grease and grime.
Remove the bottom drawer of your oven. Identify the rectangular vent on the oven door. Some ovens have vents on the top and bottom of the door; other ovens feature a vent only on the bottom. Either way, the vent is your access point to reach between the doors with your homemade cleaning tool.
Insert the cleaning tool through the vent and ensure that it can move around between the glass doors with ease. Don't jam it; you could risk getting it stuck. If it's too large for the space, remove it and make a thinner one.
Reinsert the cleaning tool through the vent and run it along the dirty glass. Expect to remove the tool and replace the cleaning surface several times, especially if the grease and grime have been on the doors for a long time.