Well, Madara knew of the original edo tensei and he still reversed Kabuto's version, which was the latest; according to the info we have so far into the story one only needs to know the hand signs and then weave them vice versa to 'free' themselves.
Logically they should do it, just to remove any possibility of Oro taking control of their bodies. And... yes, it would be plainly idiotic if Tobirama and Hashirama can't reverse edo tensei.... just imagine the dialogue...
Madara: ....and to reverse edo tensei one only needs to weave the signs backwards. Simple as!
Hashirama: Really, like that?
Tobirama: Wait, how did you do that?
I, personally, would lose all respect for Tobirama if he doesn't... -_-