What someone considers "rusty" is solely dependent on where they live. For example, to me (and many north and east of you), your car sounds "rust-free".
I am not sure why you need to wire wheel the whole bottom at this point?
I'd look into having the bottom hot pressured washed, then simply remove surface rust (patch if necc.), treat, epoxy primer, paint/undercoat.
Typically, our cars have seen some long salty, wet, snowy winters in their life, so we would want to blast or clean the underside to fix the usual bad metal, clean, derust and put a new coating on it based on what our intended use is. We generally don't drive our cars year round.
Grant