Was taught that way and never had a leaking waste joint in 15 years. Glue on pipe only, push together and twist into position. And no excess glue inside pipe.
Yup, must agree with on the pipe only and twist. Same as a copper end feed, flux on the pipe only so there's little/no flux inside the joint so little/no solder drawn inside the pipe.
A little rub with 80grit gets it clean and grippy, the glue's high enough without adding the fumes of the cleaner too