If the wrench you have only has two prongs, all the leverage you exert on the barrel nut will be focused on the two contact points. Most barrel wrenches have three or more 'prongs' (for lack of a better word) which distribute the leverage on more contact points.
If you are lucky and the barrel nut can be properly aligned with the minimum recommended 35-40 ft-pounds of torque required to tighten the nut & get the gas tube hole in the nut to line up with the hole in the upper receiver then you are good to go.
However, I have worked on some that needed FAR more than minimum torque to get the nut to align correctly. If yours happens to be one of those then I suspect you risk damaging the barrel nut by putting all the leverage on just two contact points.
My suggestion is that you try it with the two prong wrench & see if you luck out. If you do, great. If you find, however, that you are not close to getting the barrel nut properly aligned with minimum torque then you should find a proper barrel wrench with several contact points to avoid damage to the nut.