Did a few searches and in conclusion it seems that either will probably work. The question is do I need to treat the entire wall with oxalic? Treat the whole wall with F9? Or can I spot treat with F9?
I’ve done a few on concrete with oxalic but never on brick. I always treat the whole section of concrete to get a uniform appearance. Can I get away with spot treating with either f9 or oxalic on this off white brick?