I'm glad that helped clarify how flight following and two-way radio contact are basically the same thing.
Yes, class B requires explicit clearance from the radar or tower controller. One thing to keep in mind: ATC Generally tries their best to keep arriving class B aircraft inside of the airspace so that all the VFR folks flying outside can rest assured a B747 wont buzz them at close range. The controller may or may not ask you for your transition intentions. Don't assume that they will. If you're getting close to the class B and you haven't heard, let them know what you are hoping to do. You don't have to worry about a controller prompting you. Let them know your intentions ahead of time and they can take care of the rest or they'll ask you to make your request with the next controller.
To give you an idea of a flight I did last May (look at the map with San Francisco Fly):
http://skyvector.com/?ll=37.78911184817 ... :A.K2.KCCR
Took off from KCCR, requested class B clearance nearing Golden Gate Fields (VPGGF)
"Norcal Approach, Skyhawk N4902F, 2 miles east of Golden Gate Fields at 4500, request Bravo clearance for a bay tour, Planning to fly Golden gate bridge, down the shorline and returning east south of half moon bay."
They gave us a clearance to fly at 4000 even. What got interesting was as we neared SFO, they gave us vectors to avoid a B777 departure.
"Skyhawk 02F, fly heading 100, vector for departing heavy B777." We called it in sight and only when they felt it was safe they allowed us to continue southbound.
When we cleared the Bravo we were sent to the controller that handles SJC for our flight following. We called them up slightly west of the SJC charlie:
"Norcal Approach, Skyhawk 4902F, level at 4000, request touch and go at SJC."
"Skyhawk 4902F, Norcal Approach. Proceed midfield for left traffic runway 30L."
So we entered the class C since we had two-radio communication. We did a touch and go along side a landing hawker jet and then flew back to Concord. The controller asked if we had Walnut Creek in sight (the larger town south of Concord) he cancelled our flight following and we were left to our own devices flying VFR at night.
Bravo transitions really aren't that scary as long as you make your request with plenty of time to spare.