I wasn't being strictly accurate, and was a little sloppy in my phrasing. as the immediate context shows, sheng does have a nasal ng at the end, and non-mandarin chinese maintains the older consonantal endings (so cantonese has things like siu yuk which is cvv vc) but the reason I said 'cvvv pretty consistently' is that n and ng are the only viable consonant enders that remain in modern mandarin. but they do exist so my bad on the sloppiness, I was focusing on the leading head. the part that I wanted to emphasize was just that the (optional) consonantal head is single and never doubled, followed by up to three vowels. this would disallow 'glu', and contrasts with english, which sometimes allows very complicated groups of three or more consonants all together, like in the word 'strength'.
if you're looking for a pronunciation guide, sheng4 is pronounced with the sh from shot, the uh from...uh, or the a in about, and the ng from -ing, in a falling tone from high to low, like if you were saying 'Stop.' to a bunch of rowdy kids. lu4 is said in the same tone and uses a vowel that doesn't exist in english, but if you're familiar with german it is ue as you used, or the u umlaut which that represents. to say this vowel with no reference, start with loo as in waterloo or the name lou, and round your lips more and push the vowel further forward in your mouth.