Yeah, I know---when they brought out Studio 2 B the girls in the troop my grown daughter was assisting called it Girl Scouts Lite. Now with the Journeys it looks like it will be even more so.
I would just have them do the same bridging activities they always have --- have an older girl or two visit them & show them "what we do in Jrs" or whatever---or visit an older troop, or do something with an older troop at a service unit event---get the book for the next level and do some of the badge requirements from a abdge or whatever---talk about plans for next year (trips suitable for girls a year older, etc) ---and of course have them plan their bridging ceremony---the sky is the limit on that.
If you have newer leaders who are baffled by what all that means, just tell them. "It's a Girl Scout tradition to do X Y Z -- you don't have to do them all, just choose a couple and go with what works for your troop"-- and if she does not know what that means, give her some ideas.