Then its probably no problem with m-CPBA. Peracetic acid is easie to messure with syringe, reaction is done in 2min in my case. Thanks for the reference wildfyr, I give you a mole snack.
In my case I make N-oxide wich is very polar, partially water-soluble så I use DCM, the salt of benzoic acid could be soluble in in DCM, at least partially. In the referance they make epoxide.