I’ve never used the parking brake in my 4Runner since its spent its whole life in the lowcountry, which is flat.

I’m traveling to the mountains next week and might run into a scenario where I would want to use it.

Are there any specific spots that I should inspect or lubricate before trying to engage? I don’t want to run into a situation where it engages but doesn’t want to disengage

it's cable operated so you should be good. just test it if it's holding the truck and release and test if you can go. it might have enough rust in the drum.

press the parking brake halfway and drive for a few meters a few times to get those rust cleared up.

2nd going ahead and testing it before you need it. Not sure how well your parking brakes (drum brakes inside rear rotors) were adjusted at the factory in the first place and now you have a lot of age on yours. Your cable's probably fine, but it's likely that your parking brakes need to be adjusted (easy DIY job).

As for usage. I've read and always practiced engaging the parking brake before shifting into Park. At the risk of telling you something you already know, "Park" doesn't engage any sort of braking system, it's just a fixed point within in the transmission. If you use "Park" on a steep enough slope, it's actually possible the weight of the vehicle will put so much pressure on the parking pawl that you won't be able to shift back out of Park...hence applying the parking brake before shifting into Park.

Good luck.

this is what i do too. i put it in neutral, set the parking brake, release the brake so the parking brake holds the car in position and put it in park. i've never had a problem with shifting out of park.