You wanna know what to do? Start with exercising your constitutional right of keeping your mouth shut when it comes to your firearms. No officer is going to ask and unless it's in sight, no officer is going to have cause to search. Unless you give permission, the gun will remain undiscovered.
Which brings us to the question as to why you want to bring a gun into California. Unless the gun is right there, on hand, loaded and ready to shot at a moment's notice, then it's basically worthless to defend your life. If you can dig it out, load it, then shoot someone, then you could have just left the area instead.
If you just want to pass through, keep it hidden and don't discuss it with anyone.