And I did it the lazy way. Got a can of sweetened condensed milk, punched two holes in the top, put it in a pot of boiling water, and simmered away for about four hours.
It’s nearly solid – a spoon will stand straight up when stuck in it – and, OH, so good spread on ladyfingers from Trader Joe’s.
I highly recommend this super-sweet treat. Just make sure you keep an eye on the water level in the pot as it boils off. cough
Ooh, good for you! My mom used to make it the old-fashioned way.
I’ve found that there’s a Nestle brand on the bottom shelf down by the condensed milk. It’s very good.
Is the old-fashioned way very labor-intensive? I’d love to try it, but I’m…well, let’s say I’m more on the incompetent side of the cooking spectrum than the competent. 
I’ve done it that way a bunch of times, never punched holes in the top, though. It won’t explode as long as you keep it covered with boiling water. Just keep two pans going - one with the can in it, another to top off the first one when the water level drops low.
Mmmmm, dulce de leche on ice cream…
You can make it a lot faster in a pressure cooker. Only takes about a 1/2 hour. Just remove the label and boil away.
What you did was the old-fashioned way. Gail Borden worked with the Mount Lebanon Shaker community (yes, that’s as in Shaker furniture) to develop his apparatus to make condensed milk, and the Shakers promptly started using condensed milk as soon as it was available. If you look in a Shaker cookbook, you won’t see an entry for “dulce de leche”, but you will see an entry for “Mount Lebanon Pudding”.