Types of accessories and whether or not you're using switches would be good information to know.
I would personally use the internal fuse box for switched items. If you're just trying to find an IGN+ in the engine bay, I would invest in a multimeter. They're pretty inexpensive and come in very handy for any electrical work on the truck (or your home for that matter).
I am installing a Bussmann 5 relay 15303 that will have 5 switches in the cab. I thought of using the internal fuse box and have already made up the fuse tap to 5 daisy chain ends. I am thinking I can control some of the relays on the bussmann to be controlled by the ignition instead of off the 2nd battery.
Accessories are 2 lights and fridge and leave the last two switches for future use. I'll just pull the fuses for them.
I have a 2 multimeters just not with me. I'm storage in another state. That's how I brought the second one last time. I don't want to buy a third. Just thought someone might have already done this and know where in the engine fuse box it is.
Thanks for responding.