Step 1 You use the burn tool with the opacity of 50% and burn lightly under the eyes to make it look wet. The color is set to #000000 for all the actions from now on.

image (Thanks to the hot Livia for this one! )

Step 2 You take a blood brush from aleksandra's set brushes no.5, you adjust the opacity of the burn tool to 60% and midtones and apply the brush as many times as you want depending from the intensity of the tears you want. You apply them on the face directly not on a different layer:

That should be your final result. Simple right? :) I hope you found this usefull! <