I was wondering if you have to reboot the firmware every time you turn the camera on, or is there a way to turn the camera on and it's ready to shoot RAW straight off the bat.
There are two different ways to load CHDK software onto a camera - the "firmware update" and the "bootable SD card" methods. Sounds like you are using the "firmware update" method, which is easy to install on an SD card but inconvenient to actually use. The "bootable SD card" method causes CHDK to load automatically each time the camera starts but is somewhat more difficult to setup on your SD card.
Both methods are described here in detail : Prepare your SD card
There are also many methods listed there describing ways to configure your SD card. However, the use of the STICK
utilities listed at the top of the page is highly recommenced.
so basically i want to shoot in RAW on an old Powershot A series.
Be aware that the "bootable SD card" method for cameras released prior to 2011 will only work on SD cards with a 4G (or smaller) primary partition size. You'll need to use a card formatted with two partitions - one for CHDK and the other for your images - if you want to use a larger SD card. The utilities listed here will set that up for you and you can read a lot more about that on the wikia page linked here.