I live in Manhattan and I understand your frustration with getting the Jeep dirty with so many possibilities of things to dirty your vehicle, I garage mine but still when its in use on the streets, it gets dirty.
I wash it twice a week usually at this hand wash place on RT3 in NJ. Every 2 months I wash, clay bar, polish, seal, then wax. Have to clay bar every 2 months because of the tar thats on the streets in Manhattan.
Then once a year I correct the paint from the swirls, light marring. I'm due for that soon.
Find a place that does hand washing. Im not sure where you are at in NYC but I'm sure there is something in the outer boroughs that does hand washing.
And in between washings I use Meguiars ultimate quick detailer to keep it clean.
It all depends on how far you want to take it. I dont like a filthy Jeep.
Also check the detailing section here and check detailing forums like autopia.org, meguiarsonline.com, autogeek.net and get more information there.
Hope that helps.