First I got my Silhouette SD to cut out on Vinyl the letters D A D. It can be done my hand, but you dont want the letters you want the part left. So you could use the negatives of some large peel offs or negative letters from a car accessory shop. They`ll give you them FOC if you ask nicely.
Take one glass and put on the negative vinyl then cover the area with this magic paste or type glass etching into google.
Apply the paste to the glass/vinyl.
Leave for 5 minutes. I leave it longer.
The paste initially is expensive but you use a little and it lasts. I used this paste for personalised pint glasses, half glasses, and wine glasses.
For wedding anniversarys I`ve inscribed them with the people names, and 25 yrs or whatever you`d like