Target School: How do I get SA's at PE/HF/Boutiques that don't recruit on campus?

Quick question guys,

Been talking to my friend at Wharton lately and I've noticed that there are some very elite firms that conduct very exclusive on-campus recruiting there. I'm at a very strong target (not harvard or wharton though), and after a perusal of our campus career services, it's obvious these firms haven't been here in a while.

I was wondering, for someone with BB experience, and a strong resume (and willing to proactively try to get stuff), are there any mechanisms to apply to SA positions to firms like Blackstone, Moelis, CS/UBS LA, and other top notch elite groups? Submitting a resume online seems like the obvious answer--- anything on top of that? Can it be done?

Thanks in advance!