I've been trying to accomplish full independent fog light operation (with stalk switch fully functional, with parking lights and regardless of high beam state) through simply rewiring the existing relays (I don't want to fiddle with steering mounted stalks, switches or interior wiring).
There are differences between facelift model years in those electrical workshop manuals (check 2001 vs 2003 for example), so I'd recommend grabbing your multimeter, testing the relays and not fully trusting what you read.
Here's a Nissan lighting relay for reference:
The only thing you should focus on are terminals 1 and 2. Those have to be power/ground for the circuit to close and send power to the lights. It doesn't matter if terminal 1 is power or ground as long as the other terminal is the opposite. Terminal 3 will always be powered (regardless of key position) and terminal 5 sends the power out once the circuit is complete so you don't have to worry about those.
Now, you may think overriding the missing ground or power by bridging it from another relay (say, the parking lights one) is the right way to go, but I guess Nissan thought of this and made it a bit more complicated.
In my 2003 (with automatic lights), fog light relay terminals 1 and 2 behave in this manner:
Once you turn on the low beams (light switch in position 2) power is provided to terminal 1.
Once you turn on the fog light switch, ground is provided to terminal 2.
That turns the fog lights on.
Now, once you turn your high beams on:
Ground on terminal 2 is interrupted and the fog lights turn off (power is still provided to terminal 1).
If you hardwire a ground to terminal 2, you will lose the ability to use the fog light switch and the fogs will turn on (and remain on) as soon as you turn on the low beams. What you can do is remove the ability of the high beam switch to interrupt the ground and that's what I think Blindaviator did by removing the steering wheel cover, but I am trying to avoid touching those wires, so we need to keep thinking.
So, let's tackle the easiest thing first: Getting the fog lights to turn on without the need for the low beams to be on (and retain fog light switch functionality). You simply hardwire constant power to terminal 1. That'll make them work even without the parking lights which may or may not be desirable. If you want them to be tied to the parking lights, it gets a bit more complicated. The parking light relay works the opposite way of the fog light relay. You would want to bridge fog light terminal 1 and whatever terminal from the parking lights is getting power, but the parking light relay instead gets ground (not power) when you flick the switch, so that's a no go. What about terminal 5 on the parking light relay which sends out power to the parking lights once the circuit closes? Wire that to terminal 1 on the fog light relay? Bingo!
Now you have fog lights that turn on/off at will as soon as you turn on the parking lights. They will still not work with the high beams, though. For that I haven't found any solution yet that doesn't involve the steps given by Blindaviator, but combining those two things would net you fully independent fog lights.
If you don't mind not being able to use the fog light switch, you can simply bridge fog light relay terminal 2 <-> parking light relay terminal 1. The fogs will turn on with the parking lights and will remain on constantly. Note: you'll of course need to remove whatever wire is on the receiving end to avoid a feedback loop, potentially blowing up fuses and other things.
EDIT: Here's the "pics or didn't happen" part:
Testing with a piece of wire (looks awful but of course I did it properly once I confirmed my theory):
Like nothing ever happened:
Parking + fogs: