I fly the Coastal Route all the time from NorCal...easy peasy to make the climb on the way back out from SNA unless you are in a max gross 152.
Personally not a fan of the SFRA as I like to remain on FF. On the SFRA you have to cancel, frequency change, self announced, then reestablish FF on the other side in some busy airspace. For HHR and SMO it makes sense if Mini Route is closed (which it often can be based on LAX Tower Controller workload) but I have found there is plenty of time to get up/down for SNA, LGB and FUL using Coastal Route
All you need once you get handed off to your first SoCal Controller is “SoCal, Skylane 12345 level 5,500, request Coastal Route”...done. Magoo Approach or LA Center can not do anything with that request so no need to ask earlier. Unless SoCal tells you to "Remain clear of Bravo" your clearance will eventually come so start flying to the entry point. I have been right up to the blue line before getting the actual clearance. You are expected to know and fly the routes without vectors or instructions from ATC. No shortcut on entry and exit points unless vectored by ATC.
SoCal expects you to know your chit but they will hand out Bravo clearance like candy on the transitions if you are prepared. Have heard unprepared bumbling fools told to "remain clear" meanwhile I came in right behind them with clearance granted. While super helpful and cooperative, they do not have time to play ask 20 questions. I keep all the LAX routes and a "clear of Bravo" route all programmed and saved as favorites in Foreflight to pull up on a seconds notice if needed to punt...but never have.
Once SOUTH of LAX and clear the surface area however you can “request lower and direct when able” which will allow you to descend down out of the 5000’ shelf early and own nav if desired without having to fly the entire route to the exit point at altitude inside Bravo and often granted. (Generally deviations are rarely permitted north side of LAX as that is where most of the IFR flyways are)
Approach into SNA from Coastal Route I typical get cross mid field and make left traffic for 20L. Note the 15 degree offset approach you are "supposed" to fly to remain clear of the big iron approach on 20R
If you are going for a few days, consider FUL. Much easier and quicker to get in and out of and parking is only $10/night at General Aviation and first night waived with fuel. Uber is all over that area. While I have no problem with Charlie airports or Jet Center FBO's I stopped going into SNA unless I need to be right near the airport for some reason. If you go to FUL via GMN, my preferred route is GMN>KBUR>KEMT>KFUL at 3500 which brings you around and under Bravo quicker that a LAX transition. Via SBA I use the Coastal Route into SNA AND FUL.