Paul, The CA 10 day waiting period starts as soon as you complete your 4473 for the transfer and info goes into the government for your background check. If all goes well and you are approved you can pick up your firearm 10 days from that date.

the date you do the paperwork at the local FFL

Paul, it starts from the date you go to the FFL and start the paperwork/background check. Cheers and stay safe!

I am pretty sure that the waiting period starts when you go to the FFL and start the 4473 and other paperwork. If I remember correctly from when I was visiting a friend there and we stopped by his LGS, that is.