Wall street prep is not highly regarded, it’s just a useful tool for training. You’re best bet is to do Wall Street Prep, and then prep std. banking interview questions - which valuations produce highest and lowest values, what are the different valuation methods, be able to talk about an industry you might have some valuable knowledge about e.t.c. At the end of the day there are 100 other people who want to do what you want to do, so you need to figure out how to market your skill set.
I went from Electrical Engineering to private equity and then went back to b school. While i was working as an electrical engineer, with my infinite free time i took evening classes in macro econ, FSA, corp. fin e.t.c. and passed the CFA Level I exam. Then i did wall street prep. Then i interviewed for places (equity research, PE, M&A shop). For the interviews I landed, I could talk about working towards finance and making the transition.
If you already are in finance, but in some role that is middle office or something back office, then its probably going to be hard to find your desired job right now. I don’t mean to crap on the middle and back office, if i did, sorry.