. - Non-MBA masters

Non-MBA Masters are generally not well recruited by BB IBD & S&T programs. Wash U is an unlikely school for recruiting unless you are: female, black, hispanic or gay. If you're a non-black/Hispanic straight male, your best bet is a MM bank or a small prop shop (i would go smaller than your list to companies you've never heard of). These companies generally don't have the resources to recruit and hire in very small numbers. you need to network very hard to get in.

Many banks will accept quantitative master graduates in the same programs as undergrads. The visa issue makes it a bit more difficult for NY based positions. Look out for international opportunities as well.

In terms of preparation, the best thing to do is to reach out to as many contacts in the industry to really learn what it's like. One of the largest issues with quant master candidates is that they don't do their research in terms of what they will be doing. You generally won't be building regression models or getting in a lot of quant at the BB. You don't need it for IBD and in S&T you have a quant team with PHDs at MIT doing the quant for you, and you generally get paid more for adding more value trading, structure or selling.