I haven't done a lot with Bravo stuff on PE... but the way it usually works is once you ask for the Bravo entry/transition, and ATC CLEARS you into/through the bravo, and you request flight following you shouldn't have to ask for bravo entry again. That's how I see it as a rw controller (but I only work at small facility with class D primary airport).
RW pilots with lots of Bravo experience feel free to correct me!
So looking at skyvector, if you wanted to fly from SMO to POM to L35... you'd request flight following from SMO ground, they'd give you a code, you'd depart, you contact socal departure, THEN you ask for clearance into bravo at whatever altitude... say 5,500 for this flight. (This whole part might be assumed if you asked to climb to 5,500 from SMO ground, and SMO MAY coordinate the Bravo entry with socal departure). Socal clears you in to the Bravo and you shouldn't have to ask ever again.... you'll exit class B to the north east side near El Monte EMT, then they'll just keep handing you off (frequency change) to the next socal sector as you fly over the Class C @ KONT, and you could terminate FF at the east side of KONT over by KSBD... just be careful not to go through KSBD's Class D (or if you need to ask for transition from the TOWER if you're still not talking to socal)... then you'd be on your own into uncontrolled Big Bear.
It's a little confusing but basically the TRACON (socal made up of many different sectors) that covers the primary airport in class B will handle you all the way to your destination in socal airspace. It also means that whoever is "working" you in the LAX Bravo will hand you off to next controller and you don't have to ask for a C transition (because you're already talking to the controller who has jurisdiction over KONT airport/airspace - well sort of but we'll leave it at that to keep things simple). And if you stuck with socal even through SBD's Delta you wouldn't have to ask them for a D transition because the controller working you (probably from ontario sector) has jurisdiction over the Class D @ KSBD.
You could fly this route without talking to anyone except SMO ground and or tower...
Just fly @ 2000 ft departing SMO eastbound, cut to north side of KEMT's class D, and then stay to north side of Ontario's Class C, and onwards to Big Bear. Once you get on the north side of EMT you can climb to 17,500 if you really want to and top the Class C @ KONT or just stay to the north side on your way to L35.
Also FWIW, the FAA is working on new sectional charts that should be much more clear, especially in congested airspace like socal.
edit: Also if you weren't aware or don't own a sectional chart for this area use
http://skyvector.com/
It's amazingly helpful. All you do is enter KSMO in the upper left to get the map aligned with your start airport. Then select Los Angeles TAC on the upper right side of the map to open the Terminal Area Chart view...
In a nutshell just watch out for sneaky D airspace and class C's that butt up against class B... there's so much yellow it's difficult to read sometimes.