Blender 2.8 simple approach to overlaying dirt? In Blender 2.8, within the boundaries of a big rectangle I have several overlapping objects (planes and text) to which I would like to overlay a semitransparent layer of dirt.

Will this work?
(a) Create a new plane that with the same dimensions as the big rectangle
(b) Assign a .png image of dirt to the new plane
(c) Position the new plane over the big rectangle
(d) Set the transparency of the new plane as desired

If so, I would appreciate suggestions on how to
(i) make the dirt.png image appear in the new plane and
(ii) set the transparency of the dirt

Thanks in advance!
Select the plane with the Black and white dirt image and switch its blend mode and shadow mode to "Alpha something", and play with the parameters until you get the look you're looking for.