My uncle used to do that for a living, he was one of only 10 or so in the world that did back in the 70's, 80's, and early 90's. He started in the 60's I think, I remember visiting his house in the 70's and he must have had 1000's of bottles and glass things to put ships in. He even used to put them in light bulbs.
He's in his 80's now, neither of his sons bother, and those 50 years of knowledge will pass with him.