Welcome to OCDO's California forum RattleSnakeJahon! I believe most all of the information you will need to get started Open Carrying is on http://www.californiaopencarry.org.
There's also this thread
which has the UOC Pamphlet. There's a series of videos that Pullnshoot25 also made that help learn you the basics. You can find the playlist here
The first issue to address, though, is that you are 18. Technically you are "under age" to own a handgun in CA. But! As for lawful There are still options for rifles! To purchase and own a rifle one only need be 18 years of age. Although, should you choose to UOC a rifle, it stand out quite a bit more.
Keeping in mind that you mentioned you were in the wilderness areas quite often. The CA Penal Code 12031 prohibits possession of loaded firearms in public -- rifles and handguns -- with a few exemptions. One of which is that you can legally possess a firearm in unincorporated areas
where there are no discharge or load prohibitions in that county. Examples would be Kern County, National Forest areas (not National Parks!
) and BLM land.
Keeping loaded mags on your person also carries a few restrictions. For instance, you cannot carry a loaded magazine concealed on your person if you have a firearm for which that magazine or rounds go to. Speedloaders do not count. Most of us have double-mag pouches that attach to a belt.
I'm sure you'll have plenty more questions. Feel free to post them up or send some of the "veteran" Open Carriers here a private message. The CA Penal Code is the guidebook which you don't want to go against. Read up and carry on!
Speaking of which... I thought we had a "UOC Noobie thread" in this forum...