If you used it then switch to lets say dugtrio then used fissure would it automatically hit?
The next move the user uses is guaranteed to hit.
In other words no. Because Dugtrio did not use the move.
No, because it says "The next move the user uses is guaranteed to hit." So it would only work for the Pokemon who used it. Source: http://pokemondb.net/move/lock-on Hope I helped!