6mm is a big screw to go into the edge of 18mm MDF.
I've never used the superglue thread trick, but you don't want to fill a hole that big, just apply enough to the surface so that it soaks in and hardens the threads. Make sure you use a thin CA glue, and not a thick or gel version.
I'd try drilling a pilot hole 1mm undersize, and running the screw in without a tap. You might want to clamp blocks on each side before driving the screw to prevent splitting. Then apply CA.
For wood screws, it's important to pre-drill at least the root diameter of the screw.