Something Ive discovered about my Yamaha Alto is that it is quite easy to perform glissandi on it. This is a simple C to D slide-I did initially do a full scale glissando but it didnt sound great, due to the fact that I’m a mere beginner!
Michala Petri has some amazing glissando skills, on a sopranino no less. I'd imagine the smaller tone holes add to the difficulty. At 2:07 in this video.