Clamp the frames.

Distilled water in a spray bottle, small brushes.

The fragility is not in the glass but in the lead came. windex will clean the glass and not harm it, but the ammonia in it may cause the caming to further deteriorate. They really need to be restored. Distilled water is not going to remove greasy grime. I would use a cotton ball and windex and be very careful to avoid the lead between the pieces of glass,

If you have a great deal of patience, try using Q-Tips dipped in a mild cleaner, then carefully applied to the glass, avoiding the caming. Use a second Q-Tip to dry. Repeat as needed. As the glass is very old, think about supporting the glass from the underside while cleaning. This will take some time, but is worth the effort.

Thanks so much all, would a dawn solution be safe to use?

Dawn will leave a residue that needs to be rinsed. Use windex! It's meant for glass and doesn't need rinsing.