this therapy was done by my pediatrician when I was aged 12 to 15. I had a lighter form of phimosis, but the problem was, that I had additionally smegma on the penis and glans, so that my foreskin glued several times at the glans, which caused in few cases a mild form of balanitis and that the foreskin was not retractable any more.
In my teenaged time, my mom took me very often to the pediatrician because I was a sick child and had other problems (mostly abdominal) problems often. The pediatrician did always a complete full body exam from head to toe (I remember I didn´t liked that at all!), so that I always had to undress completely at the beginning, including a skin check (because I have too many moles and dysplastic nevi), genital exam (I was late at puberty, had this phimosis and a surgery of retained testicle when I was little child) and a complete hernia check (the doctor checked always my gnarly outie navel and did inguinal hernia check); the longest part was always the abdominal exam. I was brought then to several other exams like blood tests, urine sample, ecg and in some cases x-rays and ultrasound, which were done by nurses.
In the end I came back in the exam room of the doctor and had to lay down on the table again. The doctor talked to my mom about the results of ecg, x-ray and so on and in the end he did this distention therapy of my foreskin, which last a few minutes. First he pulled my foreskin back and forward several times, then he pressed with two fingers on my glans and pulled my foreskin above them and distented it with his two fingers from the inside. He repeated both methods few times and inbetween he makes a short break, while he talked to my mom or did some further more palpation of my abdomen, of my outie navel (hernia), of several moles or of my penis again. Of course it was an embarrasing thing for me (and yes I got sometimes an erection when I was aged nearly 14 to 15), but it was better than to be sent again to hospital and get surgery at my penis, my mom said.