Let me tell you that the key points are: have a plan (don’t usually invent things as you go along), hold your glass firmly with one hand, work from the bridge with the other, choose your highlighting tool with care (make your own as needed), be confident (not scratchy, unless scratchy is what you really want), consider stencils (especially if you have a repeating pattern), remember how the back of the glass is also good for stained glass highlights, and use your hands as needed (just be sure they’re clean).
Right, now I’ve said my piece, will you also have a look?