I successfully installed fastboot, but how exactly do I access the boot loader. (Sorry, just really don't want to screw up...)
It would have come up when you first booted up after installing fastboot. Afterwards you just hold home while turning on your 3ds to get to the fastboot menu where you can set up everything.
Just a quick remark... you can dump your OTP at any time via GodMode9. The bootroms are identical for *all* consoles out there (meaning: you can't really lose them). And, yeah, especially for a multi CFW setup, there's not much that would beat fastboot3ds. I may be a bit biased, though.
However the bootroms are pretty hard to find, I know I couldn't easily find them with a google search (only one result which is pretty far down and is a TOR proxy site (has .onion. in the URL). Which means you will want to be sure you have a copy otherwise you will need to reinstall b9s and then fastboot3ds again






