Layer cucumbers in a bowl, generously adding salt between each layer. Let cucumber slices rest in the refrigerator for 6-8 hours, or overnight.
After cucumbers have rested, drain off excess liquid then working in batches, squeeze out as much moisture as possible.
Combine mayo, milk, vinegar, and sugar in a medium bowl.
Add cucumbers to dressing mixture, and stir to combine.
Recipe Notes
** Cardinal Rule ** You can either serve the cucumbers immediately, or you can refrigerate them for 1-2 hours before serving. The dressing will thin out a little after they sit for a while due to the moisture in the cucumbers.