For most inks (including durabrite) try:
1/2 cup Glass cleaner
1/2 cup Alcohol *
Add 1 tbsp ammonia
* Try and use high-concentration alcohols (95% if you can). Ethanol is best, but 95% isopropyl is better than 50% ethanol. If all you can get are 50% solutions, then use 3/4 cup alcohol and 1/4 cup glass cleaner.
Most inks are water-based. To make them colourfast they use chemistry tricks and use inks that are only water soluble when the water is slightly basic. Then after they print, they react with the carbon dioxide in the air, which produces carbonic acid and neutralizes the base. This makes the ink more colourfast and less soluble in water (and harder to clean).
The above recipe uses ammonia to make it slightly basic, which helps dissolve most inks. If the glass cleaner you are using has a lot of ammonia in it, you can omit adding it and just use 50/50 glass cleaner/alcohol.