If the situation allows aircraft lighting to be on (ie peace time) then you can use the lights as a formation reference.
In my old type this meant putting the wing nav light on a cockpit light as a forward reference and using the rear nav light to control spacing along the diagonal.
More modern aircarft (such as the F18) have formation lighting strips.
In a tactical situation you will will have to rely on NVGs.
Some fleets practice both (as we did), some will just do one and some will do none.
Close formation take offs needed to be done without NVGs since the burners were too bright. Once burners were cancelled you could goggle up (easier said than done in close formation, at night - it took much practice on the ground to be able to do it right in the air!) and then carry on.
Close formation landings can be done with or without NVGs.
BV