Here is the piece of work which prompted the original query... the photo below is of a set of coal screens on one of Ian Pope's layouts (his photo, his copyright, image used here to illustrate an answer to a question).
Sorry, I cannot be sure if this is the side which Ian did or the side which was done by me - probably not relevant as we used the same raw material and applied the stuff in the same way. The roof construction is a skin of 30thou styrene supported by beams, rafters and purloins, on top of the roof layer are individual "wiggly-tin sheets" cut from 7mm corrugated iron sheets by Slater's Plastikard. I recollect that the sheets in this picture are a scale 10' x 2' in size.
I laid the lower sheets from end to end and each sheet was aligned to a line drawn along the roof layer. When the lower layer was secure I drew a feint pencil line along the top edge of the "sheets" with something like 2mm overlap. The thickness of the Slater's product (circa 20thou) needs to be taken into account when laying the second row else the top row has a mini-peak where there are four thicknesses of sheet - so I cut a notch in one (bottom) corner of each of the top row sheets so as to minimise the ups-downsy effect.
All of the wagons in this picture belong to Ian and are part of his ginormous collection of PO wagons which were found in the FoD at some point in time. There are more photos of the layout and of the wagons on Ian's Facebook page. The layout has made several appearances at model railway exhibitions this year in support of showing how the wagons were used, the range of models that are available and the research that goes into the POW books from Lightmoor Press.