On a MacBook Pro you hold down "option/alt" and hit "u" to generate the umlaut (or diaeresis), and then hit whichever vowel you want to make appear under the umlaut.
It's perfectly correct to simply write "ue" in place of "ü". Brücker and Bruecker are equally correct.
German is an odd language: "ü" = "ue" but "ue" ≠ "ü" and so forth, so that Göring = Goering, but Goethe ≠ Göthe.
Did you ever have a Christmas dinner at Escravos? I had one where the centerpiece was a roast goat with twigs for antlers, maraschino cherries for eyes, and its lips drawn back in a horrible grimace exposing its teeth. It made a vision from Hell, looking as if it died screaming and then came back to haunt us.
The locals were going down the chow line cramming as much stuff onto a plate as possible, with the Christmas cake just stuck into the side of a conical mound of rice streaming with gravy, as an afterthought.