It takes a lot of work for a woman to induce lactation. Something like like pumping for 15-30 minutes every 3-4 hours (this means even getting up in the middle of the night) for a few months straight (times are shorter if the woman has been pregnant before.) It might be possible for a man with developed breast tissue to do the same thing, but I suspect it would take even more work than it would for a woman.
If just playing with boobs increased their size, then my wife, ex-wife and several ex-girlfriends should've really grown while I was with them.