The flux in 285 solder wire is the same as 186 liquid flux, so it's rated as RMA (comes close to RA, but not quite; the flux in 44 solder wire or the 1544 liquid are more aggressive). Beyond 44 in activity level, there's 48 (most aggressive RA they offer, and IIRC, you do need to clean it).
FWIW, I use Sn62Pb36Ag2 as it's eutectic (aka 62/36/2).
You can get it in small quantities from RadioShack (add a more aggressive liquid flux should you need it).
It just says rosin, but I suspect it's at least RMA.
I picked up a couple more rolls of the .022" when a local RadioShack closed down here, so I'm probably set for life (still have most of one I bought back in the early '90's).
I also have Kester 186 and 1544 liquid flux on hand.