just do it. no fanfare, no hiding, don't look sneaky. the more naturally you go about your business, the less likely you will be to attract unwanted attention. and it all depends on your comfort level. if you are only comfortable doing it in the bathroom, then that's what you should do. but if you are are comfortable walking in and naturally removing your jacket, as anyone might as they walk into a room, then do it that way.
iwb to owb should probably be done in private just so no one sees you with gun in hand. just try to be discreet, i would do it in your car before you get out.