it is very possible to pocket train them. my one girl is bra trained and every time I open her pouch to take her out she automatically jumps into my shirt to sleep. my newer glider doesn't like to be contained to my bra space so she crawls out and sleeps in my sleeve or hood. it varies daily.
honestly, pocket training can be done, but your pocket is a very vulnerable space to put your glider and you can bump into things. their are pouches that you can purchase and you can clip them onto your pants.