After reading that write up, he did it absolutely right.
My suggestion to you, is to do this:
Get about 15 feet of 14-16ga power wire.
Get about 5 feet of 12ga ground wire.
Get a small fuse box from any parts store, you can get them in single, or multiple fuses.
You'll want some shrink wrap/electrical tape, and some connectors.
You're also going to want to get a in-line fuse, to put between the battery and the other fuse box. Say a 30 amp, depending on the fuse box rating.
From there, run the power wire through the firewall towards the battery.
Wire the positive wire to the fuse box. Then, you can connect each outlet to that fuse box.
Like I said before, those devices don't pull more than 5amps(USUALLY), so get a 5-10amp fuse for each outlet.
Join the ground wires together, then put them on the 12ga ground wire, finding a good place to secure the ground wire. There's multiple places to do this under the dash, or close to the point of where you're mounting the outlets.
You're done. Easy peasy.