What is the difference between a forward slip and a side slip?
There is no difference aerodynamically. The only difference is in intention and presence of the wind. The airplane does not care about the ground track, all it feels is the movement through the air. Both side- and forward-slip make the airplane fly slightly sideways through the air, somewhere in the direction between nose and downwards pointing wing.

If there is no wind, your ground track will be exactly the same, between wing and nose, and you will feel that the nose points away from your track and call it forward-slip. If the wind is blowing and you manage the right amount of slip, you are moving sideways through the air, but the ground track (combination of wind- and slip- movement) can be aligned exactly with the nose and you call it side-slip.

There is really no difference aerodynamically and thus no difference in applied controls either.